Bluetooth: hci_sync: Fix Opcode prints in bt_dev_dbg/err

Printed Opcodes may be missing leading zeros:

	Bluetooth: hci0: Opcode 0x c03 failed: -110

Fix this by always printing leading zeros:

	Bluetooth: hci0: Opcode 0x0c03 failed: -110

Fixes: d0b13706 ("Bluetooth: hci_sync: Rework init stages")
Fixes: 6a98e383 ("Bluetooth: Add helper for serialized HCI command execution")
Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>