arm: mvebu: turris_omnia: Implement EEPROM layout for the 'eeprom' command

Implement Turris Omnia EEPROM layout for the 'eeprom' command.

When the 'eeprom' command (with layout support) is enabled, we can now
use the 'eeprom print' and 'eeprom update' commands, for example:

  => eeprom print
  Magic constant                34a04103
  RAM size in GB                2
  Wi-Fi Region
  CRC32 checksum                cecbc2a1

Signed-off-by: Marek Behún <kabel@kernel.org>