ASoC: wm_adsp: Fix firmware file search order

Check for the cases of system-specific bin file without a
wmfw before falling back to looking for a generic wmfw.

All system-specific options should be tried before falling
back to loading a generic wmfw/bin. With the original code,
the presence of a fallback generic wmfw on the filesystem
would prevent using a system-specific tuning with a ROM
firmware.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Fixes: 0e7d82cb

 ("ASoC: wm_adsp: Add support for loading bin files without wmfw")
Link: https://msgid.link/r/20240129162737.497-2-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>