i965: make brw_wm_prog_key a little smaller

GLushort is big enough for the swizzle and origin fields.
The key could probably be made smaller still by re-ordering things.
I'll hold off on that until after the outputswritten64 branch is merged.
The key will get a little larger again with the GLbitfield64 fields.

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

@@ -74,11 +74,11 @@ struct brw_wm_prog_key {
    GLuint yuvtex_mask:16;
    GLuint yuvtex_swap_mask:16;	/* UV swaped */
 
-   GLuint tex_swizzles[BRW_MAX_TEX_UNIT];
+   GLushort tex_swizzles[BRW_MAX_TEX_UNIT];
 
    GLuint program_string_id:32;
-   GLuint origin_x, origin_y;
-   GLuint drawable_height;
+   GLushort origin_x, origin_y;
+   GLushort drawable_height;
    GLuint vp_outputs_written;
 };