gpu: ion: Move msm heaps in makefile to msm definitions

Rather than put the msm additions in the same place as generic
code in the make file, move the compilation definitions to an
msm specific definition (CONFIG_ION_MSM).

Change-Id: Icae87c43aac7c6530f50e9464000ae37e4028e04
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>