ALSA: bebob: enable to deliver MIDI messages for multiple ports

ALSA: bebob: enable to deliver MIDI messages for multiple ports

[ Upstream commit d2b6f15bc18ac8fbce25398290774c21f5b2cd44 ]

Current implementation of bebob driver doesn't correctly handle the case
that the device has multiple MIDI ports. The cause is the number of MIDI
conformant data channels is passed to AM824 data block processing layer.

This commit fixes the bug.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20210321032831.340278-4-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>