Bluetooth: switch to lock_sock in SCO

Since sco_sock_timeout is now scheduled using delayed work, it is no
longer run in SOFTIRQ context. Hence bh_lock_sock is no longer
necessary in SCO to synchronise between user contexts and SOFTIRQ
processing.

As such, calls to bh_lock_sock should be replaced with lock_sock to
synchronize with other concurrent processes that use lock_sock.

Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>