ALSA: hda: cs35l41: Remove unnecessary boolean state variable firmware_running

This state duplicates the running state inside cs_dsp, so is not necessary.
Remove it, and use cs_dsp.running instead.
This brings the CS35L41 HDA driver more inline with its ASoC version,
allowing the same state to be used when calling library functions.

Fixes: fa3efcc3

 ("ALSA: cs35l41: Use mbox command to enable speaker output for external boost")
Signed-off-by: Stefan Binding <sbinding@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20231117163609.823627-2-sbinding@opensource.cirrus.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>