ac/rgp: add missing include

The build would fail without this include if -std=gnu17 is used.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/4057
Fixes: ffdfe136e6 ("ac/sqtt: move rgp/sqtt def to ac")
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8376>

src/amd/common/ac_sqtt.h

@@ -29,6 +29,7 @@
 #include <stdint.h>
 #include <stdbool.h>
 
+#include <assert.h>
 #include "c11_compat.h"
 
 struct radeon_cmdbuf;