usb: pd: Skip decreasing current when requesting the same PPS

When a PPS PDO is selected and a request is made for the same
PDO at a different voltage, there is no need to suspend the
current draw. This allows for more efficient charging as the
charger does not have to ramp down / ramp back up its current
limit.

Change-Id: I2e5af41788b5297204a3f603a5375ec78020c919
Signed-off-by: Jack Pham <jackp@codeaurora.org>