[media] stk1160: Build as a module if SND is m and audio support is selected
As reported by Randy Dunlap:
When CONFIG_SND=m and CONFIG_SND_AC97_CODEC=m and
CONFIG_VIDEO_STK1160=y
CONFIG_VIDEO_STK1160_AC97=y
drivers/built-in.o: In function `stk1160_ac97_register':
(.text+0x122706): undefined reference to `snd_card_create'
drivers/built-in.o: In function `stk1160_ac97_register':
(.text+0x1227b2): undefined reference to `snd_ac97_bus'
drivers/built-in.o: In function `stk1160_ac97_register':
(.text+0x1227cd): undefined reference to `snd_card_free'
drivers/built-in.o: In function `stk1160_ac97_register':
(.text+0x12281b): undefined reference to `snd_ac97_mixer'
drivers/built-in.o: In function `stk1160_ac97_register':
(.text+0x122832): undefined reference to `snd_card_register'
drivers/built-in.o: In function `stk1160_ac97_unregister':
(.text+0x12285e): undefined reference to `snd_card_free'