sound: ua101: fix division by zero at probe

sound: ua101: fix division by zero at probe

Add a missing sanity check for bNrChannels in detect_usb_format()
to prevent a division by zero in playback_urb_complete() and
capture_urb_complete().

USB core does not validate class-specific descriptor fields such
as bNrChannels, so drivers must verify them before use. If a
device provides bNrChannels = 0, frame_bytes becomes zero and is
later used as a divisor in the URB completion handlers, leading
to a kernel crash.

Fixes: 63978ab3e3e9 ("sound: add Edirol UA-101 support")
Cc: stable@vger.kernel.org
Signed-off-by: SeungJu Cheon <suunj1331@gmail.com>
Link: https://patch.msgid.link/20260426111239.103296-1-suunj1331@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>