ath9k_hw: Fix XPABIAS level configuration for AR9003

Improper configuration of 0x16288 and 0x16290 would affect transmission.

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