inet: frags: remove inet_frag_maybe_warn_overflow()

This function is obsolete, after rhashtable addition to inet defrag.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 2d44ed22e607f9a285b049de2263e3840673a260)
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>