Bluetooth: Remove hci_conn_hash_lookup_state()

Since commit 4aa42119 ("Bluetooth: Remove pending ACL connection
attempts") this function is unused.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>