powerpc/mpc85xx: SECURE BOOT-Copy Boot Script on RAM

For running Chain of Trust when doing Secure Boot from NAND,
the Bootscript header and bootscript must be copied from NAND
to RAM(DDR).
The addresses and commands for the same have been defined.

Signed-off-by: Saksham Jain <saksham@freescale.com>
Signed-off-by: Ruchika Gupta <ruchika.gupta@freescale.com>
Signed-off-by: Aneesh Bansal <aneesh.bansal@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>