ALSA: snd-usb-us122l: Fix MIDI output

The US-122L always reads 9 bytes per urb unless they are set to 0xFD.

Signed-off-by: Karsten Wiese <fzu@wemgehoertderstaat.de>
Cc: stable@kernel.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>