uboot-phytec

mx28evk: Extend environment to easy write of NAND system

This adds following new targets:

 - update_nand_kernel
 - update_nand_fdt
 - update_nand_filesystem

and to avoid confusion, the 'update_nand_full' has been renamed to
'update_nand_firmware_full'.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>