gpu: ion: Add compatibility with future changes

Several changes are pending to be pulled in which are
not compatible with our changes:

* a new field to the allocation ioctl is added
* the ioctl numbers for cache flushing need to be changed.
* the size of the structure passed to ION_IOC_IMPORT
has changed

Add these changes now until full changes can be pulled
in the future.

Change-Id: I9540495e25c7b6c414a6e3719f66f2cd9f78c585
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>