drm/amdgpu/gmc8: always load MC firmware in the driver

commit b52b6738cc2d50d2a8f4d0095bcb5a86716008a5 upstream.

Some power features rely on the driver loaded version so always
load the MC firmware from the driver even if the vbios loaded
a version already.

Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>