ASoC: cs35l56-shared: KUnit tests for onchip speaker ID gpios

ASoC: cs35l56-shared: KUnit tests for onchip speaker ID gpios

Add KUnit testing of:
 cs35l56_check_and_save_onchip_spkid_gpios()
 cs35l56_configure_onchip_spkid_pads()
 cs35l56_read_onchip_spkid()

The test consists of:

- A mock regmap that simulates the pad and pin config registers.

- Parameterization of the pin list, pulls list, a simulated value for
  each pin and the speaker ID value that this should produce.

- A self-test of the simulated pin and GPIO registers.

- A test that the value returned by cs35l56_read_onchip_spkid() is
  correct.

- A test that the pin pull-up/down are set correctly by
  cs35l56_configure_onchip_spkid_pads()

- A test that cs35l56_configure_onchip_spkid_pads() and
  cs35l56_read_onchip_spkid(0 return the expected values if
  cs35l56_base->num_onchip_spkid_gpios == 0.

- A test that cs35l56_check_and_save_onchip_spkid_gpios() saves
  the configuration.

- A test that cs35l56_check_and_save_onchip_spkid_gpios() rejects
  illegal GPIO numbers.

- A test that cs35l56_check_and_save_onchip_spkid_gpios() rejects
  illegal pull types.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://patch.msgid.link/20260205164838.1611295-3-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>