drm/amdgpu: include amdgpu_video_codecs.h only where needed

drm/amdgpu: include amdgpu_video_codecs.h only where needed

Remove #include "amdgpu_video_codecs.h" from amdgpu.h and add forward declaration
of struct amdgpu_video_codecs.

Add #include "amdgpu_video_codecs.h" into files amdgpu_kms.c, amdgpu_virt.c,
cik.c, nv.c, si.c, soc15.c, soc21.c, soc24.c, soc_v1_0.c, and vi.c.

Signed-off-by: Shahyan Soltani <shahyan.soltani@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>