msm: qpnp-power-on: Add support for PON_GEN2 peripheral

Update register macros to support a new PON peripheral version.
Add code to read the PON_PERPH_SUBTYPE register and modify
functionality based on subtype value. In addition, add support
for reading the POFF_FAULT registers added in the new version.

Change-Id: Ic8f9bd8d817edca0f4762439a9e5004f8bdf0d77
Signed-off-by: Devesh Jhunjhunwala <deveshj@codeaurora.org>