ramips: add function to change rt2x00 wifi eeprom mac

Some boards like dovado tiny ac have generic ralink mac in onflash wifi eeprom.
Add eeprom_set_macaddr function to rt2x00 eeprom extract script which changes mac addr insde eeprom dump.

Signed-off-by: Andrej Vlasic <andrej.vlasic0@gmail.com>

SVN-Revision: 47347