ASoC: rt5670: Add IRQ function

This patch adds the IRQ function support of rt5670. We use a flag
named dev_gpio in platform data to inform codec driver if the IRQ
function is used or not. Also, we export rt5670_set_jack_detect
for machine driver to pass the jack point.

Signed-off-by: Bard Liao <bardliao@realtek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>