Bluetooth: hci_uart: Reorder Atheros specific driver callbacks

The driver callbacks in the Atheros support were all in a random order
and did not help readability of this driver. So reorder them to make
them aligned with what other Bluetooth UART drivers do. This patch is
not changing any actual code.

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