Fix Clang return-type error introduced with commit
96f164f6f047833091eb98a73aa80c31dc94f962 "gallium: make
pipe_context::begin_query return a boolean".
  CC       r600_query.lo
r600_query.c:443:3: error: non-void function 'r600_begin_query' should return a value [-Wreturn-type]
                return;
                ^
Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Tom Stellard <thomas.stellard@amd.com>
 
        /* Non-GPU queries. */
        switch (rquery->type) {
        case PIPE_QUERY_TIMESTAMP_DISJOINT:
-               return;
+               return true;
        case R600_QUERY_DRAW_CALLS:
                rquery->begin_result = rctx->num_draw_calls;
                return true;