ath9k_htc: Identify devices using driver_info

Categorize AR7010 & AR9287 devices based on driver_info
of usb_device_id, instead of PIDs. This avoids per-device cases
and minimize code changes for new device addition.

Signed-off-by: Rajkumar Manoharan <rmanoharan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>