power: qpnp-smbcharger: account for battery OCP for flash prediction

In the flash current prediction algorithm, the battery pack OCP
threshold was not accounted for. Use the instantaneous vbat value and
max value from the fg_adc peripheral in order to make sure the maximum
flash current reported to the flash driver is below the amount necessary
to trip OCP.

CRs-Fixed: 793302
Change-Id: I60ad0371ff530148d2d2fb9e4966767736de85e7
Signed-off-by: Xiaozhe Shi <xiaozhes@codeaurora.org>