amdgpu_fb.c

Fixes crash when trying to unload the amdgpu module before the fbdev
framebuffer was initialized, which can happen since the DRM fbdev helper
code supports deferred setup.

Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>