legacy_ion.h: a backwards-compatibility copy of ion.h

cloned from include/linux/ion.h at:

commit b6b0b65325e6f5eb5fcfd88d270f710d947f7962
Author: Brian Muramatsu <btmura@google.com>
Date:   Mon Jul 30 22:54:08 2012 -0700

    Add heap_mask to ion_allocation_data

Signed-off-by: Iliyan Malchev <malchev@google.com>
msm_ion.h: switch to using legacy_ion.h

Signed-off-by: Iliyan Malchev <malchev@google.com>
Add heap_mask to ion_allocation_data
gpu: ion: Add compatibility with future changes

Several changes are pending to be pulled in which are
not compatible with our changes. Specifically, a new
field to the allocation ioctl is added and the ioctl
numbers for cache flushing need to be 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>
Signed-off-by: Ajay Dudani <adudani@codeaurora.org>