power: qpnp-smbcharger: parallel: step reduce ICL by 100mA and rerun AICL

Currently while in parallel charging we reduce the total ICL to the
PMI's AICL result plus the current drawn from parallel charger.

The problem with this approach is that if AICL is low, we could
prematurely reduce the ICL.

Instead reduce the total ICL by 100mA per step. Also rerun AICL if the
PMI's ICL is higher than PMI's AICL result. This gives another chance
for AICL to settle higher than previous, enabling us to draw more
current.

Change-Id: I9e945ebc092d00c3b8caabb82ffa7af9d089f080
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>