(ab)Use the firmware API to store away EEPROM calibration data for

(ab)Use the firmware API to store away EEPROM calibration data for
future use by the ath(4) driver.

These embedded devices put the calibration/PCI bootstrap data on the
on board SPI flash rather than on an EEPROM connected to the NIC.
For some boards, there's two NICs and two sets of EEPROM data in the
main SPI flash.

The particulars:

* Introduce ath_fixup_size, which is the size of the EEPROM area in
  bytes.
* Create a firmware image with a name based on the PCI device identifier
  (bus/slot/device/function).
* Hide some verbose debugging behind 'bootverbose'.

ath(4) can then use this to load in the EEPROM data.

This requires AR71XX_ATH_EEPROM to be defined.