Explicitly include "gcstruct.h" for GCOps

Should fix https://github.com/ssvb/xf86-video-sunxifb/issues/14


and prevent FTBFS on some systems.
Reported-by: Fred Chien <cfsghost@gmail.com>
Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>

src/sunxi_x_g2d.c

@@ -34,6 +34,7 @@
 #include "dri2.h"
 #include "damage.h"
 #include "fb.h"
+#include "gcstruct.h"
 
 #include "fbdev_priv.h"
 #include "sunxi_x_g2d.h"