[ALSA] Fix dependency of snd-adlib driver in Kconfig

Added the missing dependency on CONFIG_SND for snd-adlib driver.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>
diff --git a/sound/isa/Kconfig b/sound/isa/Kconfig
index 557c4de..57371f1 100644
--- a/sound/isa/Kconfig
+++ b/sound/isa/Kconfig
@@ -13,6 +13,7 @@
 
 config SND_ADLIB
 	tristate "AdLib FM card"
+	depends on SND
 	select SND_OPL3_LIB
 	help
 	  Say Y here to include support for AdLib FM cards.