ALSA: hdspm: Replace tasklet with work

ALSA: hdspm: Replace tasklet with work

The tasklet is an old API that should be deprecated, usually can be
converted to another decent API.  In HDSP-MADI driver, a tasklet is
still used for offloading the MIDI I/O handling (optional via mixer
switch).  It can be achieved gracefully with a work queued, too.

This patch replaces the tasklet usage in HDSP-MADI driver with a
simple work.  The conversion is fairly straightforward.  The only
significant difference is that the work initialization is moved to the
right place in snd_hdspm_create() and cancel_work_sync() is always
called in snd_hdspm_free() to assure killing the pending works.

Link: https://lore.kernel.org/r/20200903104131.21097-8-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>