sock: redo the psock vs ULP protection check

In the Linux kernel, the following vulnerability has been resolved:

sock: redo the psock vs ULP protection check

Commit 8a59f9d1e3d4 ("sock: Introduce sk->sk_prot->psock_update_sk_prot()")

has moved the inet_csk_has_ulp(sk) check from sk_psock_init() to

the new tcp_bpf_update_proto() function. I'm guessing that this

was done to allow creating psocks for non-inet sockets.

Unfortunately the destruction path for psock includes the ULP

unwind, so we need to fail the sk_psock_init() itself.

Otherwise if ULP is already present we'll notice that later,

and call tcp_update_ulp() with the sk_proto of the ULP

itself, which will most likely result in the ULP looping

its callbacks.