drm/amdgpu: take the mode_config mutex when handling hpds
drm/amdgpu: take the mode_config mutex when handling hpds

Since we may modify display state.

Reviewed-by: Christian König <c7ea837d7a46effe4232b086213468b8b31643bf@amd.com>
Signed-off-by: Alex Deucher <08dc22c6156113f2deff178e35e3ed9b24d6af9e@amd.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs