ALSA: usb-audio: Fix a limit check in proc_dump_substream_formats()

This should be ARRAY_SIZE() instead of sizeof().  The sizeof() limit is
too high so it doesn't work.

Fixes: 093b8494

 ("ALSA: usb-audio: Print more information in stream proc files")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20200422092255.GB195357@mwanda
Signed-off-by: Takashi Iwai <tiwai@suse.de>