regulator: kryo-regulator: program LDO Vref register before switching modes

The LDO Vref register must be set prior to triggering a mode switch,
even if the value programmed in the Vref register has not changed.
Call kryo_set_ldo_volt() when changing modes to satisfy this
requirement.

Change-Id: I43ab9c59046fc9a5915cdc8f54f1e2821b047a34
Signed-off-by: Osvaldo Banuelos <osvaldob@codeaurora.org>