ARM: dts: msm: Add separate CMA region for modem mba for MSM8916

On 3GB msm8916 targets, DDR base starts from 0x4000_0000
and common CMA region is allocated within lowmem. Modem
MBA which allocates memory from common CMA however expects
its memory > 0x8000_0000.

Create a separate CMA region to satisfy modem MBA needs
which is allocate towards higher addresses.

Change-Id: I0c02dbc5f2c4b14e13b2d6c5b42c81c06f5dfdd0
Signed-off-by: Rajkumar Raghupathy <raghup@codeaurora.org>
Signed-off-by: Taniya Das <tdas@codeaurora.org>
Signed-off-by: Bharat Pawar <bpawar@codeaurora.org>
Signed-off-by: Nirmal Abraham <nabrah@codeaurora.org>