ion: ioctl compatibility with userland using old api

As far as I can tell, flags passed by userland are now used to determine
buffer caching.

Note in ION_IOC_ALLOC_COMPAT we are currently forcing uncached buffer
allocations (needed to make a choice here).  This
may need to change.

Signed-off-by: Flemmard <flemmard@gmail.com>
gpu: ion: Fix flags passed from userspace in COMPAT ioctl

 * We need to honor both cached and uncached mappings.

Change-Id: Iacddd1903fc8dcb2c93871346af54fa58f2b014e