ASoC: rt5645: Prevent the pop sound of the headphone while rebooting or shutdowning

Add i2c shutdown function to prevent the pop sound of the headphone while
the system is rebooting or shutdowning. It de-initials the jack detection
function, and it cannot be turned off in _BIAS_OFF. If we don't de-initial
it, the pop sound will be heard in the situation of powering off. And
replace the related register settings from magic number to meaningful
defined name.

Signed-off-by: Oder Chiou <oder_chiou@realtek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>