Add handling of the "spk-id-gpios" _DSD property. If present, the
value indicated by the GPIOs is appended to the subsystem-id
part of the firmware name to load the appropriate tunings for that
speaker.

Some manufacturers use multiple sources of speakers, which need
different tunings for best performance. On these models the type
of speaker fitted is indicated by the values of one or more GPIOs.
The number formed by the GPIOs identifies the tuning required.

The speaker ID is only used in combination with a _SUB identifier
because the value is only meaningful if the exact model is known.

The code to get the speaker ID value has been implemented as a
new library so that the cs35l41_hda driver can be switched in
future to share common code. This library can be extended for
other common functionality shared by Cirrus Logic amp drivers.
Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20230918095129.440-2-rf@opensource.cirrus.comSigned-off-by: Takashi Iwai <tiwai@suse.de>