Bluetooth: ISO: lock sk in iso_connect_ind

Bluetooth: ISO: lock sk in iso_connect_ind

Accessing iso_pi(sk)->conn requires lock_sock, which is not taken in the
"ev3" part of iso_connect_ind.  It may also be NULL if socket has
transitioned away from the LISTEN/CONNECT states before locking.

Fix by adding lock/release. Recheck hcon is valid after lock acquire
where needed.

Fixes: 168d9bf9c7f0 ("Bluetooth: ISO: Reassemble PA data for bcast sink")
Signed-off-by: Pauli Virtanen <pav@iki.fi>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>