ath9k_htc: Dump base eeprom header for UB91/94/95

Debugfs file location: <debugfs_mnt>/ieee80211/phy#/ath9k_htc/base_eeprom

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