i965: Move the WM input sizes calculation to emit() time.

It's used for program compile.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Acked-by: Paul Berry <stereotype441@gmail.com>

src/mesa/drivers/dri/i965/brw_vs_constval.c

@@ -237,6 +237,6 @@ const struct brw_tracked_state brw_wm_input_sizes = {
       .brw   = BRW_NEW_VERTEX_PROGRAM | BRW_NEW_INPUT_DIMENSIONS,
       .cache = 0
    },
-   .prepare = calc_wm_input_sizes
+   .emit = calc_wm_input_sizes
 };