rgtc: llvmpipe/softpipe refuse RGTC until u_format has support.

So far I haven't implemented the u_format code for these.

Signed-off-by: Dave Airlie <airlied@redhat.com>

src/gallium/drivers/llvmpipe/lp_screen.c

@@ -278,6 +278,11 @@ llvmpipe_is_format_supported( struct pipe_screen *_screen,
       return util_format_s3tc_enabled;
    }
 
+   /* u_format doesn't support RGTC yet */
+   if (format_desc->layout == UTIL_FORMAT_LAYOUT_RGTC) {
+      return FALSE;
+   }
+
    /*
     * Everything else should be supported by u_format.
     */

src/gallium/drivers/softpipe/sp_screen.c

@@ -248,6 +248,11 @@ softpipe_is_format_supported( struct pipe_screen *screen,
       return util_format_s3tc_enabled;
    }
 
+   /* u_format doesn't implement RGTC yet */
+   if (format_desc->layout == UTIL_FORMAT_LAYOUT_RGTC) {
+	return FALSE;
+   }
+
    /*
     * Everything else should be supported by u_format.
     */