ALSA: us122l: Use snd_card_free_when_closed() at disconnection

ALSA: us122l: Use snd_card_free_when_closed() at disconnection

The USB disconnect callback is supposed to be short and not too-long
waiting.  OTOH, the current code uses snd_card_free() at
disconnection, but this waits for the close of all used fds, hence it
can take long.  It eventually blocks the upper layer USB ioctls, which
may trigger a soft lockup.

An easy workaround is to replace snd_card_free() with
snd_card_free_when_closed().  This variant returns immediately while
the release of resources is done asynchronously by the card device
release at the last close.

The loop of us122l->mmap_count check is dropped as well.  The check is
useless for the asynchronous operation with *_when_closed().

Fixes: 030a07e44129 ("ALSA: Add USB US122L driver")
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20241113111042.15058-3-tiwai@suse.de