ion: Fix compat support to use proper compat ioctl numbers

The compat support added to ion didn't provide compat ioctl numbers
(who's value depends on the compat structure size). So 32bit
applications would get an error when trying to make ioctl calls.

This patch adds the needed COMPAT_ macros and uses them in the
compat_ion_ioctl, translating them to their non-compat cmd when
calling the normal ioctl call.

Change-Id: I53636d4ec46d8dc5e694697aaf2d62b98bd78cb1
Signed-off-by: John Stultz <john.stultz@linaro.org>