power: qpnp-smbcharger: Correct ibatt calculation for ESR pulse

Battey current is negative most of the time when charging, use the
absolute value for calculating the fast charge current need to be set
during ESR pulse. And also correct the value in units of uA to mA.

CRs-Fixed: 1012390
Change-Id: I97767b1f7fb9adbd90fb73c913b4c00002c2c7cc
Signed-off-by: Fenglin Wu <fenglinw@codeaurora.org>