power: qpnp-smbcharger: support configuring fast charge current dynamically

During parallel charging, there might be a need to configure
fast charge current dynamically. If the fast charge current is
less than 1800 mA, then do the configuration only on main
charger and suspend the parallel charger. If the fast charge
current is more than 1800 mA, then configure the charge current
on both main and parallel chargers with half of that value.

CRs-Fixed: 782147
Change-Id: I1c66349ea3b35a9871f2fa77c71c534061c70529
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>