ARM: dts: msm: Add cpu context, scan dumps to mem-dump node for Bengal

Currently cpu context and cpu scan dump entries are getting added
from watchdog driver. As part of unification support for the mem-dump
table entries, move cpu context and scan dumps entries to mem-dump
node for Bengal target.

Change-Id: I6e835bc3e79e171325c64d8b35642f969241099b