selftests: cgroup: Fix missing newline in test_zswap_writeback_one

Fixes malformed test output due to missing newline

Signed-off-by: Sebastian Chlad <[e-mail]>
Signed-off-by: Tejun Heo <[e-mail]>

tools/testing/selftests/cgroup/test_zswap.c

···
 		return -1;
 
 	if (wb != !!zswpwb_after) {
-		ksft_print_msg("zswpwb_after is %ld while wb is %s",
+		ksft_print_msg("zswpwb_after is %ld while wb is %s\n",
 				zswpwb_after, wb ? "enabled" : "disabled");
 		return -1;
 	}