libgralloc: Use ION_IOC_CUSTOM instead of MSM-specific ioctls

Use ION_IOC_CUSTOM instead of ION_IOC_CLEAN_INV_CACHES.
ION_IOC_CLEAN_INV_CACHES is now specified as a command argument of the
ION_IOC_CUSTOM ioctl.

Change-Id: I5b59ba1032364dfb884a90abf2ee2b35f3c09dd6
1 file changed