power: pm8921-charger: do not open OVP FETs in CHG_GONE ISR

When the CHG_GONE interrupt is triggered do not open the OVP
FETs of USB or DC. This causes connection resets for USB and DC.
This should only be initiated by the unplug_check_worker which
checks more conditions before opening the OVP FETs and thus
avoids unnecessary disconnections events.

Change-Id: Iee06155aa41c782e2b2fed4acf3b44ee038c1c23
Signed-off-by: David Keitel <dkeitel@codeaurora.org>