ARM: dts: msm: Add system PM device binding for Lito

System PM device handles all activities supporting the SoC's
capability to enter system sleep modes. Add device bindings
for this.

Change-Id: I10fc6885d4b3a82054cb68818715117a73f11d4c
Signed-off-by: Srinivas Rao L <lsrao@codeaurora.org>
Signed-off-by: Maulik Shah <mkshah@codeaurora.org>