drm/amdgpu: fix location of prototype for amdgpu_kms_compat_ioctl

This fixes the warning below by changing the prototype to a location
that's actually included by the .c files that call
amdgpu_kms_compat_ioctl:

warning: no previous prototype for ‘amdgpu_kms_compat_ioctl’
[-Wmissing-prototypes]
37 | long amdgpu_kms_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
| ^~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Isabella Basso <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu.h

···
 u32 amdgpu_get_vblank_counter_kms(struct drm_crtc *crtc);
 int amdgpu_enable_vblank_kms(struct drm_crtc *crtc);
 void amdgpu_disable_vblank_kms(struct drm_crtc *crtc);
-long amdgpu_kms_compat_ioctl(struct file *filp, unsigned int cmd,
-			     unsigned long arg);
 int amdgpu_info_ioctl(struct drm_device *dev, void *data,
 		      struct drm_file *filp);
 

drivers/gpu/drm/amd/amdgpu/amdgpu_drv.h

···
 long amdgpu_drm_ioctl(struct file *filp,
 		      unsigned int cmd, unsigned long arg);
 
+long amdgpu_kms_compat_ioctl(struct file *filp,
+			     unsigned int cmd, unsigned long arg);
+
 #endif