fsl-mpc8315e-rdb: Enable EEPROM

Update the mpc8315erdb.dts to contain the eeprom device
information. Coupled with adding "MISC_DEVICES" into the
kernel configuration, we have a working eeprom.

Signed-off-by: Jingdong Lu <jingdong.lu@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>