ath9k_hw: Fix AR_GPIO_INPUT_EN_VAL_BT_PRIORITY_BB and its shift value in 0x4054

The bit value of AR_GPIO_INPUT_EN_VAL_BT_PRIORITY_BB is wrong, it should
be 0x400 and the number of bits to be right shifted is 10. Having this
wrong value in 0x4054 sometimes affects bt quality on btcoex environment.

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