ath5k: initialize eeprom struct early on attach

This fixes this sparse warning:

  CHECK   drivers/net/wireless/ath/ath5k/attach.c
drivers/net/wireless/ath/ath5k/attach.c:288:42: warning: symbol 'ee' shadows an earlier one
drivers/net/wireless/ath/ath5k/attach.c:109:34: originally declared here

Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>