ENGR00255111 battery: fix voltage decreased only while discharging

ENGR00255111 battery: fix voltage decreased only while discharging

If system run higher cpu loading with bigger current, such as GPU or VPU,
the voltage of battery will decrease down quickly  and rise up later.But the
battery driver only permit voltage decreasing while discharging before, in
other words, in the above case , the voltage will keep in very low level,
although the voltage will rise back again.

Now, remove the constrain in the code. Of course, with the patch, voltage will
down and rise back when run high loading user case, but it's better than
LOW ALWAYS, in worst case, the battery capacity will be 0 as test team reported

Please note :
Current battery capaity is not accurate because of hardware
design defect(ENGR00219632) on Sabresd.So please ignore the accuracy issue.

Signed-off-by: Robin Gong <b38343@freescale.com>