ASoC: wm_adsp: Add support for loading bin files without wmfw

A self-booted DSP may have a file of coefficients to apply to the device
even when there is no firmware to download.

Signed-off-by: Simon Trimmer <simont@opensource.cirrus.com>
Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20230320112245.115720-7-rf@opensource.cirrus.com


Signed-off-by: Mark Brown <broonie@kernel.org>