ALSA: line6: Perform sanity check for each URB creation

LINE6 drivers create stream URBs with a fixed pipe without checking
its validity, and this may lead to a kernel WARNING at the submission
when a malformed USB descriptor is passed.

For avoiding the kernel warning, perform the similar sanity checks for
each pipe type at creating a URB.

Reported-by:  <syzbot+c190f6858a04ea7fbc52@syzkaller.appspotmail.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/s5hv9iv4hq8.wl-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>