package/flac: drop unrecognized option

xmms-plugin has been dropped since version 1.4.2 and
https://github.com/xiph/flac/commit/8fbeff238c41464fe220cd23c45861c9302d1172

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/flac/flac.mk

@@ -17,7 +17,6 @@ FLAC_CONF_OPTS = \
 	$(if $(BR2_POWERPC_CPU_HAS_ALTIVEC),--enable-altivec,--disable-altivec) \
 	$(if $(BR2_INSTALL_LIBSTDCPP),--enable-cpplibs,--disable-cpplibs) \
 	$(if $(BR2_POWERPC_CPU_HAS_VSX),--enable-vsx,--disable-vsx) \
-	--disable-xmms-plugin \
 	--disable-stack-smash-protection
 
 ifeq ($(BR2_PACKAGE_LIBOGG),y)