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

Added the missing dependency on CONFIG_SND for snd-adlib driver.
Signed-off-by: NTakashi Iwai <tiwai@suse.de>
Signed-off-by: NJaroslav Kysela <perex@suse.cz>

sound/isa/Kconfig

@@ -13,6 +13,7 @@ config SND_CS4231_LIB
 
 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.