ARM: dts: msm: Add nvmem devices on PMK8350 to support PPG

PWMs on PM8350C require the nvmem devices SDAM21 and SDAM22 to store
pattern data as well as per-channel data. Add the required devices to
PMK8350 so that they may be referenced and used by the PWM node.

Change-Id: I762ff0c81ed7855d52231be81b8e08abfef5e708