Bluetooth: Add hdev helper variable to hci_le_create_connection_cancel

The hci_le_create_connection_cancel() function needs to use the hdev
pointer in many places so add a variable for it to avoid the need to
dereference the hci_conn every time.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>