gpu: ion: Flush the chunk list before passing it to trustzone

Previously, the function scm_call used to take care of flushing
the caches to ensure all data was written back to memory before
going into the secure world. The behavior of scm_call is changing
such that clients are expected to flush caches themselves. Since
the address that the chunk list is written to is cached, we need
to ensure that the data is actually written back. Add the appropriate
cache operations on the chunk list.

Change-Id: I05e6fa868409255e66f1f37f98199c5a7e81882c
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>