ath9k: Re-order functions in main.c

Some of the functions in main.c are re-ordered in such
a way that all local functions are defined before mac80211
and pci callbacks.
Signed-off-by: Vasanthakumar Thiagarajan <vasanth@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>