ARM: dts: msm: Add modem heap and migrate 8916 memory regions to CMA

PIL driver needs ION heap to support relocatable feature.
Pass modem memory region as ION heap. Also, CMA now
fully supports removing regions from memory. Since CMA
is the preferred method for tracking these regions
as well, migrate all removed regions over to use
CMA and CMA derivatives.

Change-Id: If3673e7533f5d526daa559ba6fe655d4f6092b14
Signed-off-by: Susheel Khiani <skhiani@codeaurora.org>