drm/radeon/evergreen: Move 'cik_*()'s prototypes to shared header

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

drivers/gpu/drm/radeon/cik.c:6413:6: warning: no previous prototype for ‘cik_init_cp_pg_table’ [-Wmissing-prototypes]
6413 | void cik_init_cp_pg_table(struct radeon_device *rdev)
| ^~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/radeon/cik.c:6670:5: warning: no previous prototype for ‘cik_get_csb_size’ [-Wmissing-prototypes]
6670 | u32 cik_get_csb_size(struct radeon_device *rdev)
| ^~~~~~~~~~~~~~~~
drivers/gpu/drm/radeon/cik.c:6702:6: warning: no previous prototype for ‘cik_get_csb_buffer’ [-Wmissing-prototypes]
6702 | void cik_get_csb_buffer(struct radeon_device *rdev, volatile u32 *buffer)
| ^~~~~~~~~~~~~~~~~~

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/cik.h

···
 int ci_mc_load_microcode(struct radeon_device *rdev);
 void cik_update_cg(struct radeon_device *rdev, u32 block, bool enable);
 u32 cik_gpu_check_soft_reset(struct radeon_device *rdev);
+void cik_init_cp_pg_table(struct radeon_device *rdev);
+u32 cik_get_csb_size(struct radeon_device *rdev);
+void cik_get_csb_buffer(struct radeon_device *rdev, volatile u32 *buffer);
 
 #endif                         /* __CIK_H__ */

drivers/gpu/drm/radeon/evergreen.c

···
 
 #include "atom.h"
 #include "avivod.h"
+#include "cik.h"
 #include "ni.h"
 #include "rv770.h"
 #include "evergreen.h"
···
 void evergreen_fini(struct radeon_device *rdev);
 void evergreen_pcie_gen2_enable(struct radeon_device *rdev);
 void evergreen_program_aspm(struct radeon_device *rdev);
-void cik_init_cp_pg_table(struct radeon_device *rdev);
-
-extern u32 cik_get_csb_size(struct radeon_device *rdev);
-extern void cik_get_csb_buffer(struct radeon_device *rdev, volatile u32 *buffer);
 
 static const u32 evergreen_golden_registers[] =
 {