lpm.rc init: Fix charger mode and update pm paths.

lpm.rc is only processed by init when the device boots into charger
mode. In charger mode, init does not trigger the 'early-boot' and 'boot'
actions at all. It runs the 'charger' action instead.

Before this patch even core services were not started in charger mode,
as class_start was part of the non-existing 'boot' action.

Insert usecases for different platforms and add pm paths for msm8974
to init.qcom.lpm_boot.sh

Change-Id: I2d1e794a5a288abca33a59a00ae49ef02d111950
(cherry picked from commit ad66f016f0ca31b049a777dca9e9e5b66afbc5b5)