[ALSA] Fix no mpu401 interface can cause hard freeze

This patch fixes the remaining instances in our tree where a non-
existent mpu401 interface can cause a hard freeze when i/o is issued.
This commit closes Malone #34831.
Bug: https://launchpad.net/distros/ubuntu/+source/linux-source-2.6.15/+bug/34831
patch location:
http://www.kernel.org/git/?p=linux/kernel/git/bcollins/ubuntu-dapper.git;a=commitdiff;h=b422309cdd980cfefe99379796c04e961d3c1544


From: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>