msm: qpnp-power-on: Add support for PON Rev B

PON S2 control register contents are split into two
registers - s2 control and s2 control2 in Rev B PON
module. Add support to choose correct registers based
on PON revision.

CRs-fixed: 480430
Change-Id: I90a3c7a5a3424cfebd5fcf66567047dec1bad011
Signed-off-by: Mohan Pallaka <mpallaka@codeaurora.org>