ARM: mvebu: clearfog: add Clearfog GTR support

Select the serdes configuration table based on the platform identity
read from EEPROM TLV data. Clearfog GTR needs a slightly different
serdes configuration.

Reviewed-by: Stefan Roese <sr@denx.de>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>