gpu: ion: Add support for securing indiviudal buffers

Newer protection APIs allow individual allocations to be secured
instead of the entire heap. Add APIs to support securing individual
Ion handles. These APIs include a flag option to support delaying
the unsecure until the buffer itself is actually freed.

Change-Id: I01e2bc921a342e4bb6191a642942264a9613d6f9
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>