gpu: ion: export needed functions for PVR SGX

Make ion symbols visible to kernel modules. The SGX DDK
in modular form requires these symbols to be exported.

The reason for the code movement of ion structs is due to
EXPORT_SYMBOL’s requirement that the storage size of all
function parameters is known. This is so that the kernel can
sanity-check the size of data structures at module load time.

Change-Id: I2b9efe285557268da3baf258af09b56917add920
Signed-off-by: Rogelio Garcia <rgarcia@ti.com>
ion: omap: change behaviour of getting buffers from pvr fd

previous implemention shares the pvr ion client and the ion
handles associated with that client for a particular pvr fd.
now, we just call ion_share on the handles and return the
shared buffers. caller is in charge of calling ion_import using
its own ion client to get the ion handles.

Change-Id: I2abdee1daed7b5c57c66b2e5fddc4eb0d0cc1305
Signed-off-by: Tyler Luu <tluu@ti.com>