power: qpnp-charger: report CURRENT_MAX for battery

Report the maximum current property that is calculated
by the BMS based on battery voltage and battery resistance.

If BMS is not available this property is always zero.

Change-Id: I015572e17477661d4952c9fc195de2609fd9dc34
Signed-off-by: David Keitel <dkeitel@codeaurora.org>