ARM: dts: msm: Add smem configuration for sdxprairie

Add new entry in device tree for smem region. This smem
region is used to pass data to remote processors.

Change-Id: Idc700b9997703a1fdcd41e9afe20f3332c7777df
Acked-by: Gaurang Parikh <gparikh@qti.qualcomm.com>
Signed-off-by: Chris Lew <clew@codeaurora.org>