board: phytec: am62x: Add support for 1 & 4 GB RAM variants

Use content of EEPROM to detect the actual RAM size and adjust
DDR timings, size and banks accordingly.
Also enable the SoM detection per default in the defconfigs.

Signed-off-by: Wadim Egorov <w.egorov@phytec.de>
Tested-by: John Ma <jma@phytec.com>
6 files changed