drm_hwcomposer: Fix all cases which triggers an error on -Wsign-compare

Android-9 has -Wsign-compare enabled by default and it causes build issues.
Enable -Wsign-compare option in CI, so we won't introduce such issues anymore.

Signed-off-by: Roman Stratiienko <roman.o.stratiienko@globallogic.com>
4 jobs for fix-sign-compare-for-pie in 10 minutes and 13 seconds (queued for 19 seconds)