power: pm8921-bms: fix fake battery emulation

With the recent split of functions to calculate and report state of
charge, the faking battery feature broke, it remained in the calculate
function.

Move the fake battery feature in the reporting function, where it really
belongs.

Change-Id: Ibc2ecdbca32911b4f35c7e6c2278631a614227fa
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>