ARM: dts: msm: Add 512MB based device variants for 8916

Add 512MB variant for all 8916 devices since certain memory
optimizations are needed in device tree to meet the required
performance for such low memory targets. These optimizations
are not needed for >512MB targets.

CRs-fixed: 639052
Change-Id: Id24db76511aaed5f6782c2c21c16d0cc6b1aee38
Signed-off-by: Kishan Kumar <kishank@codeaurora.org>
Signed-off-by: Aparna Mallavarapu <aparnam@codeaurora.org>