gradient: Disable gradient for gles2.

As PVR glsl compiler seems doesn't support external fragment
function, and fails at compile gradient shader. Disable it
for now. We may need to modify gradient shader to don't use
external function.

Signed-off-by: Zhigang Gong <zhigang.gong@linux.intel.com>

glamor/glamor.c

@@ -399,7 +399,9 @@ glamor_init(ScreenPtr screen, unsigned int flags)
 	glamor_init_tile_shader(screen);
 	glamor_init_putimage_shaders(screen);
 	glamor_init_finish_access_shaders(screen);
+#ifdef GLAMOR_GRADIENT_SHADER
 	glamor_init_gradient_shader(screen);
+#endif
 	glamor_pixmap_init(screen);
 
 	glamor_priv->flags = flags;

glamor/glamor_priv.h

@@ -741,8 +741,8 @@ glamor_poly_line(DrawablePtr pDrawable, GCPtr pGC, int mode, int npt,
 
 #define GLAMOR_PIXMAP_DYNAMIC_UPLOAD
 #define GLAMOR_DELAYED_FILLING
+#ifndef GLAMOR_GLES2
 #define GLAMOR_GRADIENT_SHADER
-
-
+#endif
 
 #endif				/* GLAMOR_PRIV_H */