i965/vec4: Add missing doxygen close brace.

Reviewed-by: Eric Anholt <eric@anholt.net>

src/mesa/drivers/dri/i965/brw_vec4.h

@@ -261,6 +261,7 @@ public:
     */
    const void *ir;
    const char *annotation;
+   /** @} */
 
    bool is_send_from_grf();
    bool can_reswizzle_dst(int dst_writemask, int swizzle, int swizzle_mask);