ASoC: rt5640: Add rt5640_set_ovcd_params() helper

Some devices don't use the builtin jack-detect but can still benefit
from the mic-bias-current over-current-detection to differentiate
between headphones vs a headset.

Move the ovcd init code from rt5640_enable_jack_detect() into a new
rt5640_set_ovcd_params() helper and export this helper as well
as a couple of related ovcd functions.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20210819190543.784415-5-hdegoede@redhat.com
Signed-off-by: Mark Brown <broonie@kernel.org>