msm8916-wcd-analog uses button0 to differentiate between headphone and
headset. Under some circumstances, button pressed and released
interrupts are not fired as the driver expects it.

For instance, with some connectors, there are spurious button-pressed
interrupts when unplugging a headphone, without the corresponding
button-released interrupt. But the codec always alternates between
button pressed and released interrupts, it cannot fire two interrupts of
the same kind in a row. That means that when the headphone is plugged
back, only a button-released interrupt will be fired instead of pressed
then released. This causes the driver to report headphone as headset.

By changing the logic and relying on button 0 release interrupt, the
driver could be made more robust for connectors that differ from the one
used on the Dragonboard's audio mezzanine.
Signed-off-by: Damien Riegel <damien.riegel@savoirfairelinux.com>
Signed-off-by: Mark Brown <broonie@kernel.org>