board: phytec: am572x_phycore_rdk: set the board_name dynamically
The board_name env variable is updated dynamically from the
kit_opt data stored on the SOM's EEPROM data and then used
to determine the correct device tree file to load with the
If there is no data stored in the EEPROM, the EEPROM is not
populated, or the EEPROM data is invalid, the system will
default to the platform default of "am572x_phycore_rdk"
Signed-off-by: Russell Robinson <email@example.com>