ARM: dts: msm: configure default CMA region for sdm630

Configure the size of the default CMA region to 32 MB in
DT for sdm630.

Configuring the default CMA region in the DT is cleaner
than using CONFIG_CMA_SIZE_MBYTES since it is easier to
configure per target and the alloc ranges can be specified
in DT.

Change-Id: I329ae0aa9cffeed7c30e44749c15fbb83c58b599
Signed-off-by: Shiraz Hashim <shashim@codeaurora.org>