ARM: dts: msm: Add RTB trace support for msmferrum

Add rtb support to device tree node which enables RTB logging on msmferrum.
RTB logging provides useful debug information by logging events to
uncached buffer which can be processed from ramdumps in case of device
reset.

Change-Id: I5daf1db828eedf0dd6a79b63233c067da34df551
Signed-off-by: Xiaogang Cui <xiaogang@codeaurora.org>