ARM: dts: msm: add PM8937, PMI8937 and PMI8940 PMIC peripheral devices

Add new device tree files pm8937, pmi8937.dtsi and pmi8940.dtsi
which contain devices for the PMIC peripherals found in PM8937,
PMI8937 and PMI8940 chips.

These files are based upon msm-pm8937.dtsi, msm-pmi8937.dtsi and
msm-pmi8940.dtsi found in msm-3.18 branch as of:

'commit c0b3f609196f ("ARM: dts: msm: Remove GPU mempool for msm8909")'

CRs-Fixed: 2160311
Change-Id: I0ca62064c54ede929aa921618260c58868b738f4
Signed-off-by: Tirupathi Reddy <tirupath@codeaurora.org>