ARM: dts: msm: add dynamic refresh memory for msm8996

Add memory region for dynamic refresh rates where the pll
codes are stored by the bootloader. The data in this memory
region is read during MDSS PLL driver's probe.

Change-Id: I735e9a9993c2ca57a9b5d00188fed1de9fb34b33
Signed-off-by: Jeevan Shriram <jshriram@codeaurora.org>