For GFX v9_4_3, set MTYPE_UC for memory access over PCIe.

v4 - add missing indentation pointed out by Felix and add his
reviewed-by tag.
v3 - add missing logic for the svm path.
v2 - add amdgpu_xgmi_same_hive to separate access over xgmi from pcie
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Amber Lin <Amber.Lin@amd.com>
Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>