drm/msm: use the right pgprot when mapping BOs in the kernel

Use the same logic as the userspace mapping.

This fixes msm_rd with cached BOs.

Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Acked-by: Jordan Crouse <jordan@cosmicpenguin.net>
Link: https://lore.kernel.org/r/20210423190833.25319-4-jonathan@marek.ca


Signed-off-by: Rob Clark <robdclark@chromium.org>