drm/amdgpu: fix documentation warning

Fixes this issue:
drivers/gpu/drm/amd/amdgpu/amdgpu_device.c:5094: warning: expecting prototype for amdgpu_device_gpu_recover_imp(). Prototype was for amdgpu_device_gpu_recover() instead

Fixes: cf727044 ("drm/amdgpu: Rename amdgpu_device_gpu_recover_imp back to amdgpu_device_gpu_recover")
Reviewed-by: Kent Russell <kent.russell@amd.com>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>