qcom-charger: smblib: add support for pd current setting

Forcing a certain current limit is not supported in the current
driver, but well needed in when pd is active.

In this change, ICL_OVERRIDE/APSD and USB mode are updated, so
that PD can alter current limit by simply voting the ICL
setting.

Change-Id: I8d3ec938d433fe9bdbb8c091873c07e75c49d632
Signed-off-by: Harry Yang <harryy@codeaurora.org>