As 3G/1G user/kernel memory split is used on LS1021A, the Linux kernel
fails to access the device tree blob on boot. The reason is that u-boot
relocates the device tree blob into high memory when booting the kernel
and the kernel is unable to access the blob.

To avoid this issue, fdt_high is set to the value of 0xffffffff. The
device tree blob will not get relocated and is still in low memory to
make it accessible to the kernel.

For the same reason, initrd_high is set to the value of 0xffffffff too.
Signed-off-by: NAlison Wang <alison.wang@freescale.com>
Reviewed-by: NYork Sun <yorksun@freescale.com>