am335x, dxr2: get ECC sType from I2C eeprom

read the ECC Type field from the i2c eeprom, instead
configuring it static in the U-Boot binary.

see RM:
Table 26-17. NAND Geometry Information on I2C EEPROM

Signed-off-by: Heiko Schocher <hs@denx.de>