ath9k: avoid using trinary operator w/ TX_STAT_INC

Otherwise, you get this:

  CC [M]  drivers/net/wireless/ath/ath9k/hif_usb.o
drivers/net/wireless/ath/ath9k/hif_usb.c: In function ‘ath9k_skb_queue_complete’:
drivers/net/wireless/ath/ath9k/hif_usb.c:230:12: error: expected expression before ‘do’
make[2]: *** [drivers/net/wireless/ath/ath9k/hif_usb.o] Error 1
make[1]: *** [drivers/net/wireless/ath/ath9k] Error 2
make: *** [drivers/net/wireless/ath/] Error 2

The TX_STAT_INC macro should probably be changed to accomodate such
usage, although using a trinary operator in place of an if-else seems
questionable to me anyway.

Signed-off-by: John W. Linville <linville@tuxdriver.com>
Acked-by: Sujith Manoharan <Sujith.Manoharan@Atheros.com>