Revert "bpf: Fix potential call bpf_link_free() in atomic context"

This reverts commit 31f23a6a18.

This change made many selftests/bpf flaky: flow_dissector, sk_lookup, sk_assign and others.
There was no issue in the code.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

kernel/bpf/syscall.c

@@ -2345,8 +2345,12 @@ void bpf_link_put(struct bpf_link *link)
 	if (!atomic64_dec_and_test(&link->refcnt))
 		return;
 
-	INIT_WORK(&link->work, bpf_link_put_deferred);
-	schedule_work(&link->work);
+	if (in_atomic()) {
+		INIT_WORK(&link->work, bpf_link_put_deferred);
+		schedule_work(&link->work);
+	} else {
+		bpf_link_free(link);
+	}
 }
 
 static int bpf_link_release(struct inode *inode, struct file *filp)