egl-helpers: fix display init for x11

When running on gtk we need X11 platform not mesa platform.
Create separate functions for mesa and x11 so we can keep
the egl #ifdef mess local to egl-helpers.c

Fixes: 0ea1523fb6703aa0dcd65e66b59e96fec028e60a
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 20170505104101.30589-4-kraxel@redhat.com
diff --git a/ui/gtk-egl.c b/ui/gtk-egl.c
index 89492c0..cf48cca 100644
--- a/ui/gtk-egl.c
+++ b/ui/gtk-egl.c
@@ -246,7 +246,7 @@
     GdkDisplay *gdk_display = gdk_display_get_default();
     Display *x11_display = gdk_x11_display_get_xdisplay(gdk_display);
 
-    if (qemu_egl_init_dpy(x11_display) < 0) {
+    if (qemu_egl_init_dpy_x11(x11_display) < 0) {
         return;
     }