gpu: ion: support begin/end and kmap/kunmap dma_buf ops

These ops were added in the 3.4 kernel.  This patch adds support
for them to ion.  Previous ion_map/unmap_kernel api is also
retained in addition to this new api.

Change-Id: I6d2db284dce12c2d8cc4e540865beee2da43bd0c
Signed-off-by: Rebecca Schultz Zavin <rebecca@android.com>