bytcr-rt5640: Add support for a second headphones output

bytcr-rt5640: Add support for a second headphones output

Some devices (HP Elitepad 1000 G2) have a second headphones output
(1 on the dock, 2nd on the tablet itself) which is implemented through
the line-out output of the codec combined with an external hp-amp.

The kernel has recently gotten support for this setup and will
advertise this to userspace by adding cfg-hp2:lineout to the
components string, add support for this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>