madvise06: Add tag for "mm: memcg: link page counters to root ..."

The test may trigger a warning if bf4f059 is present (5.9) and
use_hierarchy=0 which is fixed by 8de15e920dc8. Full details of the
bug are in the kernel commit description and I do not want to repeat
them in the test description as they are likely to be irrelevant to
most readers.

Signed-off-by: Richard Palethorpe <[email protected]>
Reviewed-by: Li Wang <[email protected]>

testcases/kernel/syscalls/madvise/madvise06.c

@@ -235,6 +235,7 @@ static struct tst_test test = {
 	.needs_root = 1,
 	.tags = (const struct tst_tag[]) {
 		{"linux-git", "55231e5c898c"},
+		{"linux-git", "8de15e920dc8"},
 		{}
 	}
 };