ASoC: wm_adsp: Convert '/' to '-' when normalizing firmware filenames

ASoC: wm_adsp: Convert '/' to '-' when normalizing firmware filenames

Don't preserve '/' in firmware filename fields - convert it to '-' like
other punctuation characters.

The code originally normalized the entire string, including the
directory prefix. To prevent breaking the directory it had to preserve
'/' characters in the name, but this meant that the system name and ALSA
prefix must not contain those characters.

It's trivial to skip the directory name prefix and start the
normalization after it, and that means the normalization does not need
to make a special case for '/'.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://patch.msgid.link/20260310141817.1871794-8-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>