Due to a HW bug, the system memory mappings and peer GPU mappings
on GFX12 need to be marked as MTYPE_NC.

Cc: Joe Greathouse <joseph.greathouse@amd.com>
Cc: David Belanger <david.belanger@amd.com>
Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@amd.com>
Signed-off-by: Sreekant Somasekharan <sreekant.somasekharan@amd.com>
Reviewed-by: Harish Kasiviswanathan <Harish.Kasiviswanathan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>