ARM: dts: msm: Add RTB logging dt entry on SDXPRAIRIE

Add devicetree entry for initializing RTB logging driver and trace
register access which helps during debugging on sdxprairie target.

Change-Id: I0d00435817547dc3bc8fd6ffc42f843b1811922c
Signed-off-by: Jeevan Shriram <jshriram@codeaurora.org>