drm/radeon/radeon_gem: Move 'radeon_gem_prime_*()'s prototypes to shared header

Fixes the following W=1 kernel build warning(s):

drivers/gpu/drm/radeon/radeon_prime.c:34:18: warning: no previous prototype for ‘radeon_gem_prime_get_sg_table’ [-Wmissing-prototypes]
34 | struct sg_table *radeon_gem_prime_get_sg_table(struct drm_gem_object *obj)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/radeon/radeon_prime.c:42:7: warning: no previous prototype for ‘radeon_gem_prime_vmap’ [-Wmissing-prototypes]
42 | void *radeon_gem_prime_vmap(struct drm_gem_object *obj)
| ^~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/radeon/radeon_prime.c:55:6: warning: no previous prototype for ‘radeon_gem_prime_vunmap’ [-Wmissing-prototypes]
55 | void radeon_gem_prime_vunmap(struct drm_gem_object *obj, void *vaddr)
| ^~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/radeon/radeon_prime.c:62:24: warning: no previous prototype for ‘radeon_gem_prime_import_sg_table’ [-Wmissing-prototypes]
62 | struct drm_gem_object *radeon_gem_prime_import_sg_table(struct drm_device *dev,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/radeon/radeon_prime.c:86:5: warning: no previous prototype for ‘radeon_gem_prime_pin’ [-Wmissing-prototypes]
86 | int radeon_gem_prime_pin(struct drm_gem_object *obj)
| ^~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/radeon/radeon_prime.c:104:6: warning: no previous prototype for ‘radeon_gem_prime_unpin’ [-Wmissing-prototypes]
104 | void radeon_gem_prime_unpin(struct drm_gem_object *obj)
| ^~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/radeon/radeon_prime.c:120:17: warning: no previous prototype for ‘radeon_gem_prime_export’ [-Wmissing-prototypes]
120 | struct dma_buf *radeon_gem_prime_export(struct drm_gem_object *gobj,
| ^~~~~~~~~~~~~~~~~~~~~~~

Cc: Alex Deucher <[e-mail]>
Cc: "Christian König" <[e-mail]>
Cc: David Airlie <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Signed-off-by: Lee Jones <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/radeon/radeon_gem.c

···
 #include <drm/radeon_drm.h>
 
 #include "radeon.h"
+#include "radeon_prime.h"
 
 struct dma_buf *radeon_gem_prime_export(struct drm_gem_object *gobj,
 					int flags);

drivers/gpu/drm/radeon/radeon_prime.c

···
 #include <drm/radeon_drm.h>
 
 #include "radeon.h"
+#include "radeon_prime.h"
 
 struct sg_table *radeon_gem_prime_get_sg_table(struct drm_gem_object *obj)
 {

drivers/gpu/drm/radeon/radeon_prime.h

···
+/* radeon_prime.h -- Private header for radeon driver -*- linux-c -*-
+ *
+ * Copyright 2012 Advanced Micro Devices, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * PRECISION INSIGHT AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ */
+
+#ifndef __RADEON_PRIME_H__
+#define __RADEON_PRIME_H__
+
+struct dma_buf *radeon_gem_prime_export(struct drm_gem_object *gobj,
+					int flags);
+struct sg_table *radeon_gem_prime_get_sg_table(struct drm_gem_object *obj);
+int radeon_gem_prime_pin(struct drm_gem_object *obj);
+void radeon_gem_prime_unpin(struct drm_gem_object *obj);
+void *radeon_gem_prime_vmap(struct drm_gem_object *obj);
+void radeon_gem_prime_vunmap(struct drm_gem_object *obj, void *vaddr);
+
+#endif				/* __RADEON_PRIME_H__ */