deconfig: msm8610: Reduce default CMA region to 4MB

Reduce the size of CMA region from 16MB to 4MB to
allow for more unmovable pages in the system which
will help in low-memory conditions.

Change-Id: Id3caefc9e75c2423b08a179534f073e4742abda9
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>