xserver-xorg: disable SDL kdrive server

Otherwise the build breaks if the SDL package is enabled, as xserver's
configure script detects SDL support, but doesn't find our sdl-config
script, so linking fails.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

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

@@ -70,7 +70,8 @@ XSERVER_XORG_SERVER_CONF_OPT += --disable-xorg
 endif
 
 ifeq ($(BR2_PACKAGE_XSERVER_tinyx),y)
-XSERVER_XORG_SERVER_CONF_OPT += --enable-kdrive --enable-xfbdev --disable-glx --disable-dri
+XSERVER_XORG_SERVER_CONF_OPT += --enable-kdrive --enable-xfbdev \
+		--disable-glx --disable-dri --disable-xsdl
 else
 XSERVER_XORG_SERVER_CONF_OPT += --disable-kdrive --disable-xfbdev
 endif