mesa3d: ensure it can only be compiled with modular X server

kdrive has no glx support, and mesa3d depends on libdrm which needs
largefile support (just like the modular server), so ensure mesa3d
can only be enabled in that configuration.

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

package/x11r7/mesa3d/Config.in

@@ -8,6 +8,7 @@ config BR2_PACKAGE_MESA3D
 	select BR2_PACKAGE_LIBDRM
 	select BR2_PACKAGE_EXPAT
 	depends on BR2_PACKAGE_XSERVER_XORG_SERVER
+	depends on BR2_PACKAGE_XSERVER_xorg
 	depends on BR2_INSTALL_LIBSTDCPP
 	help
 	  Mesa 3D, an open-source implementation of the OpenGL specification.