ARM: dts: msm: add PMIC PWM devices for PMA8084

Add device tree nodes to support the PWM/LPG devices found in
PMA8084 PMIC chips.

Also disable PMA8084 PWM devices for MSM8974Pro-AC targets which
utilize PM8941 chips so that the there are no duplicate PWM
channel ID values.

Change-Id: I7496277f3ee43cb723e75b8e898e7898cc1077ec
Signed-off-by: David Collins <collinsd@codeaurora.org>