power: qpnp-qg: Report instantaneous-IBAT if averaged-IBAT is not ready

The averaged-IBAT holds the reset value 0x8000 (which corresponds to
5A/10A max supported QG current) if its read before the fist-ever fifo
is complete. In such a case report the instantaneous IBAT.

Change-Id: I65b3c93ad2cb54d82356907c809c70b0414036d1
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>