power: qpnp-qg: Update CURRENT_NOW for parallel charging

The last_fifo_i alternately samples the current
from internal BAT_FET and parallel charger. Instead
use the FIFO_I average while reporting CURRENT_NOW
when parallel charging is enabled.

While at it, use the RTC time as the FIFO timestamp for
better co-relation during debug.

Change-Id: Iaaf445809b1b0096cc74b5d62c2510640f0482ad
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>