ath9k_hw: Fix regression of register offset for AR9003 chips

My recent commits (3782c69d, 324c74a) introduced regression
for register offset selection that based on the macversion.
Not using parentheses in proper manner for ternary operator
leads to select wrong offset for the registers.

This issue was observed with AR9462 chip that immediate disconnect
after the association with the following message

ieee80211 phy3: wlan0: Failed to send nullfunc to AP 00:23:69:12:ea:47
after 500ms, disconnecting.

Cc: stable@kernel.org
Signed-off-by: Rajkumar Manoharan <rmanohar@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>