ixgbe: change the eeprom version reported by ethtool

Use 32bit value starting at offset 0x2d for displaying the firmware
version in ethtool. This should work for all current ixgbe HW

Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Stephen Ko <stephen.s.ko@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>