mpd: force zeroconf to no

without this we get missing dependecy errors if avahi is staged.

Signed-off-by: John Crispin <blogic@openwrt.org>

sound/mpd/Makefile

 	--disable-wavpack \
 	--disable-wildmidi \
 	--disable-zzip \
-	--with-zeroconf=auto \
+	--with-zeroconf=no \
 	\
 	--enable-curl \
 	--enable-flac \