drm/amdgpu/dce6: Set MASTER_UPDATE_MODE to 0 in resume_mc_access as well

Looks like this was missed when dce_v6_0.c was added.

Fixes: e2cdf640 ("drm/amdgpu: add display controller implementation for si v10")
Reviewed-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>
Cc: stable@vger.kernel.org