gralloc: Cleanup usage of old API

All builds have now moved to the new ION API.

Change-Id: Ic5ed7aa40231be64c715d6bb0d00a022db3fb863
gralloc: Use new ION API by default

This conditionally reverts commit b519bb243a1537f7420a2e81bbfa91d38d4ae8dc
and reverses the logic to use OLD_ION_API since NEW_ION_API
is the default.

Change-Id: I3708dff82207844302431296ccfc29421d104442