ARM: dts: msm: reserve memory for display ramdump for sm8150

Reserve memory for display ramdump feature on
sm8150 target. This memory buffer would be
configured by the bootloader and needs to be retained forever.

Change-Id: If31a6d04a847b5a86aa29e861b55c52c5a99efb4
Signed-off-by: Narendra Muppalla <NarendraM@codeaurora.org>