ARM: dts: msm: Add DT entry to reserve memory for splash

To reserve physical memory address for splash on msm8939,
add memory node DT parameter in 8939 common DT file. This
physical address is used for updating splash screen until
the first update comes from user space. Update the same
reserve from MDSS DTSI for both 8916 and 8939.

Change-Id: I93a15e744db85526661f3bef6b8940257ddf1e7f
Signed-off-by: Jayant Shekhar <jshekhar@codeaurora.org>