ALSA: line6: toneport: Fix broken usage of timer for delayed execution

The line6 toneport driver has code for some delayed initialization,
and this hits the kernel Oops because mutex and other sleepable
functions are used in the timer callback.  Fix the abuse by a delayed
work instead so that everything works gracefully.

Reported-by:  <syzbot+a07d0142e74fdd595cfb@syzkaller.appspotmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>