ARM: dts: msm: add PM8998 PMIC peripheral devices

Add a new device tree file pm8998.dtsi which contains devices
for the PMIC peripherals found in PM8998 chips.

This file is based upon msm-pm8998.dtsi found in the msm-4.4
branch as of:

commit b8c4038d1470 ("Merge "msm: mdss: Handling possible
integer overflow"").

Change-Id: I04caa5bc25b6a24929a76d20d9e52419f4e23833
Signed-off-by: David Collins <collinsd@codeaurora.org>