Bluetooth: fix bt_accept_dequeue() to work in process context

No local_bh_disable is needed there once we run everything in process
context. The same goes for the replacement of bh_lock_sock() by
lock_sock().

Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>