[ALSA] more section mismatches

Something about __init_or_module isn't working as expected (?).
CONFIG_HOTPLUG=y
CONFIG_MODULES=n
Fix shared init/exit code helper:
WARNING: sound/built-in.o(.exit.text+0x243): Section mismatch: reference to .init.text: (between 'alsa_card_mpu401_exit' and 'ac97_bus_exit')
WARNING: sound/built-in.o(.exit.text+0x21b): Section mismatch: reference to .init.text: (between 'alsa_card_dummy_exit' and 'alsa_card_serial_exit')

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