ALSA: emux: Use standard print API

Use the standard print API with dev_*() instead of the old house-baked
one.  It gives better information and allows dynamically control of
debug prints.

Some functions are changed to receive snd_card object for calling
dev_*() functions, too.

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20240807133452.9424-44-tiwai@suse.de