ion: Remove custom compat framework

It was pointed out that there is no need for a custom compat ioctl
framework in Ion, that decision can all be handled in device
registration. Remove the custom compat framework and just handle
the decision regarding compat ioctls in msm_ion.c

Change-Id: I6a0791013ce8e1f2f679555a46afd33de8fd9ce6
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>