minigbm: gralloc0: Remove BO_USE_HW_CAMERA_ZSL

minigbm: gralloc0: Remove BO_USE_HW_CAMERA_ZSL

In gralloc0, the flag GRALLOC_USAGE_HW_CAMERA_ZSL is defined to be a
bitwise OR of GRALLOC_USAGE_HW_CAMERA_WRITE and
GRALLOC_USAGE_HW_CAMERA_READ. So it is incorrect to treat it as a
separate usage flag, not even thinking about using it with the bitwise
AND operator for conditional tests.

Fix the current broken state by removing BO_USE_HW_CAMERA_ZSL, which
does not have any reason to exist.

BUG=b:62358788
TEST=Camera preview renders correctly on Poppy.

Change-Id: I883713f7e1c82c7747b20ac2000fb2edd5207616
Reviewed-on: https://chromium-review.googlesource.com/561034
Commit-Ready: Tomasz Figa <tfiga@chromium.org>
Tested-by: Tomasz Figa <tfiga@chromium.org>
Reviewed-by: Ricky Liang <jcliang@chromium.org>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>