ASoC: rt5651: Do not modify jd and PLL power bits from set_bias_level()

rt5651_set_bias_level(BIAS_OFF) used to unconditionally clear the entire
register, including the jack-detect and PLL power bits. When jack-detection
support was introduced a special case for jack-detect was added which
hard-codes a register value to keep both on.

This commit removes the jack-detect special case, instead simply leaving
these bits as is on BIAS_OFF.

Tested-by: Carlo Caione <carlo@endlessm.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mark Brown <broonie@kernel.org>