hwmon: boost_dynamic_controller: correct votes to RPM according to VPH

Currently, votes according to VPH to RPM is wrong. We should vote RPM
according to below rules. If the VPH is larger than ceiling threshold,
we should vote 0 for boot regulstor to RPM.  If the VPH is less than
floor threshold, we should vote 1 for boot regulstor to RPM. Hence
update the driver accordingly.

Change-Id: I29d7d769bd1c438791864321522701b5b7659449
Signed-off-by: Ke Liu <keliu@codeaurora.org>