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

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

Change-Id: I3fbe37c8f07aa80041ddaf37998bea8a1bd5af5a
Signed-off-by: Krishna Manikandan <mkrishn@codeaurora.org>