power: qcom: smb-lib: optimize parallel current limiting with PD

In MID-MID parallel charging configuration the parallel charger needs to
be limited such that it does not draw more power than the input can
provide. Currently the limiting algorithm assumes that the input voltage
when using PD is always 5V, but if the input voltage changes then the
limiting algorithm would unnecessarily limit the parallel charge
current.

Fix this by using the PD input voltage as an input to the limiting
algorithm.

Change-Id: I5a59ce11f0e802c982e944598fe61bad43e36779
Signed-off-by: Nicholas Troast <ntroast@codeaurora.org>