power: qpnp-smbcharger: expose CURRENT_MAX prop via batt psy

Expose CURRENT_MAX property as it is a required battery power
supply property.

CRs-Fixed: 2068899
Change-Id: Ib46c0c73e0e298d35b7d671f87c8cd67e328e017
Signed-off-by: Tirupathi Reddy <tirupath@codeaurora.org>
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>