regulator: qpnp-regulator: add support for FTS 2.5 type regulators

Add support for QPNP PMIC FTS 2.5 type regulators.  This type of
regulator supports auto mode control, auto phase control, and
three phases enabled at one time.  The FTS 2.5 voltage mapping is
similar to that of existing FTS 2 except for an additional
offset.

Change-Id: I8c8a3498896fab795d3151a61e19c5b62bd02c2e
Signed-off-by: David Collins <collinsd@codeaurora.org>