Add reboot notifier to each codec so that it can do some workarounds
needed for reboot.

So far, patch_sigmatel.c calls its shutup routine for avoiding noises
at reboot on some HP machines.

References: Novell bnc#544779
	http://bugzilla.novell.com/show_bug.cgi?id=544779Signed-off-by: NTakashi Iwai <tiwai@suse.de>