power: qpnp-qg: Update PON_OCV and GOOD_OCV handling

The QG HW state machine based on the reset / PON conditions
updates the PON SOC at different HW registers. Add the SW
logic to read the PON SOC from LAST_S3 / SDAM / S7_PON
registers.

While at it, enable the GOOD_OCV IRQ only when APPS is not
in sleep.

Change-Id: I1083fe96865c52820a1212882121b4c7f7c8db63
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>