mpd: disable libsoup

this showed up during the BB build

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

sound/mpd/Makefile

@@ -116,6 +116,7 @@ CONFIGURE_ARGS += \
 	--disable-pulse \
 	--disable-sidplay \
 	--disable-solaris-output \
+	--disable-soup \
 	--disable-sqlite \
 	--disable-twolame-encoder \
 	--enable-wave-encoder \