drm/msm: replace MSM_BO_UNCACHED with MSM_BO_WC for internal objects

msm_gem_get_vaddr() currently always maps as writecombine, so use the right
flag instead of relying on broken behavior (things don't actually work if
they are mapped as uncached).

Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Acked-by: Jordan Crouse <jordan@cosmicpenguin.net>
Link: https://lore.kernel.org/r/20210423190833.25319-3-jonathan@marek.ca


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