gma500: Don't try and take a GEM handle of a non GEM fb

The initial GMA500 framebuffer is not GEM but stolen memory. We can't
therefore take a GEM handle of it. Stop anyone trying to do this and causing
a crash.

Ideally we need a way to have GEM handles to non GEM objects but it's not
clear how and if GEM and the modesetting/fb interfaces it provides are
supposed to or indeed if they can handle it.
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/gma500/psb_fb.c

@@ -648,6 +648,8 @@ static int psb_user_framebuffer_create_handle(struct drm_framebuffer *fb,
 {
         struct psb_framebuffer *psbfb = to_psb_fb(fb);
         struct gtt_range *r = psbfb->gtt;
+        if (r->stolen)
+                return -EOPNOTSUPP;
         return drm_gem_handle_create(file_priv, &r->gem, handle);
 }