package/x11r7/xserver_xorg-server: drop unrecognized option

dmx has been dropped since version 21.1.0 and
https://gitlab.freedesktop.org/xorg/xserver/-/commit/b3b81c8c2090cd49410960a021baf0d27fdd2ab3

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/x11r7/xserver_xorg-server/xserver_xorg-server.mk

@@ -45,7 +45,6 @@ XSERVER_XORG_SERVER_CONF_OPTS = \
 	--disable-config-hal \
 	--enable-record \
 	--disable-xnest \
-	--disable-dmx \
 	--disable-unit-tests \
 	--with-builder-addr=buildroot@buildroot.org \
 	CFLAGS="$(TARGET_CFLAGS) -I$(STAGING_DIR)/usr/include/pixman-1 -O2" \
@@ -165,10 +164,6 @@ else
 XSERVER_XORG_SERVER_CONF_OPTS += --disable-screensaver
 endif
 
-ifneq ($(BR2_PACKAGE_XLIB_LIBDMX),y)
-XSERVER_XORG_SERVER_CONF_OPTS += --disable-dmx
-endif
-
 ifeq ($(BR2_PACKAGE_OPENSSL),y)
 XSERVER_XORG_SERVER_CONF_OPTS += --with-sha1=libcrypto
 XSERVER_XORG_SERVER_DEPENDENCIES += openssl