opencv: gtk support doesn't work with directfb

This was dropped on 4b3d949b8af240bda451b0a4e57d60153188c2e4 when
libgkt2 was updated. Fixes:
http://autobuild.buildroot.net/results/817/8173b7fd3d6af79a7f2c04bf36059a4429127516/

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/opencv/Config.in

@@ -150,7 +150,7 @@ comment "gstreamer support requires a toolchain with WCHAR and threading support
 
 config BR2_PACKAGE_OPENCV_WITH_GTK
 	bool "gtk support"
-	depends on BR2_PACKAGE_XORG7||BR2_PACKAGE_DIRECTFB
+	depends on BR2_PACKAGE_XORG7
 	depends on BR2_USE_WCHAR # libgtk2 -> libglib2
 	depends on BR2_TOOLCHAIN_HAS_THREADS # libgtk2 -> libglib2
 	depends on BR2_INSTALL_LIBSTDCPP