i915: report GBM_BO_MAP_CACHE_WC for scanout

If a bo has BO_USE_SCANOUT, and it is ever scanned out, the kernel
driver changes its cache level to WC.  But the change is not reflected
in the guest.  Let's be conservative and report GBM_BO_MAP_CACHE_WC when
BO_USE_SCANOUT is set.

BUG=b:323433235
TEST=Squid works properly with cross-domain on volteer

Change-Id: I9325ffc0cfef8778917e13d5021ae884ac7a6dfb
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/minigbm/+/5255422
Reviewed-by: Dominik Behr <dbehr@chromium.org>
Tested-by: Yiwei Zhang <zzyiwei@chromium.org>
Commit-Queue: Yiwei Zhang <zzyiwei@chromium.org>
1 file changed