ath9k: Clean up few function parameters in recv.c

ath9k_rx_skb_preprocess() needs only ieee80211 frame header,
pass only frame headers instead of skb to that function. Also
remove ineffective frame dump in ath9k_process_rate().

Signed-off-by: Vasanthakumar Thiagarajan <vasanth@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>