regulator: rpmh-regulator: add support for PMIC5 regulator modes

The MODE_CTL register values corresponding to each mode are
different between PMIC4 and PMIC5 regulators.  Add support for
the values utilized by PMIC5 regulators.

Change-Id: I5f3a1a0380f684a1d855ce80c9edf0412079a623
Signed-off-by: David Collins <collinsd@codeaurora.org>