ALSA: ac97_patch make functions static

Only used in ac97_codec by including ac97_patch.c directly, effectively static

Found by sparse:
sound/pci/ac97/ac97_patch.c:3551:5: warning: symbol 'patch_vt1617a' was not declared. Should it be static?
sound/pci/ac97/ac97_patch.c:3767:5: warning: symbol 'patch_vt1618' was not declared. Should it be static?

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>