[ADS5121] Support for the ADS5121 board

The following MPC5121e subsystems are supported:

- low-level CPU init
- NOR Boot Flash (common CFI driver)
- DDR SDRAM
- FEC
- I2C
- Watchdog

Signed-off-by: Grzegorz Bernacki <gjb@semihalf.com>
Signed-off-by: Rafal Jaworowski <raj@semihalf.com>
Signed-off-by: Jan Wrobel <wrr@semihalf.com>