Bluetooth: hci_uart: Fix typo in stats for sco tx

s/stat.cmd_tx++/stat.sco_tx++ for HCI_SCODATA_PKT

Signed-off-by: Karl Beldan <karl.beldan@gmail.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>