android: ion: add nozero and sync_force flags

android: ion: add nozero and sync_force flags

Allocation with ION_FLAG_NOZERED returns buffers without clearing data
written by previous users. ION should not allow userspace accessing
the buffer due to the security reason.
ION_FLAG_SYNC_FORCE is also introduced for some users that want to
decide the point of cache maintenance by itself. With the flag, ION
performs cache flush to the allocated even for cached buffers. those
users want this redundant cache flush to prevent buffer corruption by
victim dirty cache lines about the buffer after DMA write without
proper cache maintenance.

Change-Id: Ib3c4f9c93a6cd0240ae12b8c061142355e2b1605
Signed-off-by: Cho KyongHo <pullip.cho@samsung.com>