mesa/st: reduce size of state->st bitmask

In d035d50 this changed to 64b.. which I'm pretty sure was
unintentional.  Revert it back to 32b so the entire state struct
is a nice round 64b.

(Note sure that it would actually be measurable, but I did notice
that check_state() was hot in some benchmarks.)

Signed-off-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>

src/mesa/state_tracker/st_context.h

@@ -70,7 +70,7 @@ struct u_upload_mgr;
 
 struct st_state_flags {
    GLbitfield mesa;  /**< Mask of _NEW_x flags */
-   uint64_t st;      /**< Mask of ST_NEW_x flags */
+   uint32_t st;      /**< Mask of ST_NEW_x flags */
 };
 
 struct st_tracked_state {