r600g: Fix Clang return-type build error.

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>
diff --git a/src/gallium/drivers/radeon/r600_query.c b/src/gallium/drivers/radeon/r600_query.c
index 28a814a..71f4a15 100644
--- a/src/gallium/drivers/radeon/r600_query.c
+++ b/src/gallium/drivers/radeon/r600_query.c
@@ -440,7 +440,7 @@
 	/* 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;