power: qpnp-charger: remove chg_done ISR

The chg_done interrupt has proven to be ineffective
to determine the actual end of charge.

In the following series software end of charge
logic will be added to more accurately determine the
end of charge.

Change-Id: Ia6294fb121f4b45eced4e38f76384156740b6081
Signed-off-by: David Keitel <dkeitel@codeaurora.org>