defconfig: Align sdm660 arm32 defconfig with arm64

Align arm32 and arm64 sdm660 defconfig with respect to
iommu configs and remove cma size selection as it is to be
moved to device tree.

Change-Id: I5c5f88c05dce9f58d29d56d9cfea2b0d785d665a
Signed-off-by: Shiraz Hashim <shashim@codeaurora.org>