ath9k: Fix bug in reading input gpio state for ar9003

The register which gives input gpio state is 0x404c for ar9003,
currently 0x4048 is wrongly used. This will disable RF and make
it unusable on some of AR9003.

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