uboot-imx

MA-16594-1 Set dtb load offset in bootloader

We use the 'second_addr' in boot image header to store the
fdt load address which is set by '--second_offset' parameter,
but actually we don't pass any 'second' image to it. Now the
mkbootimg.py will check the 'second' image size and set the
'second_addr' as 0x0 if no 'second' image is specified.

Since we don't store dtbs in the boot.img (except recovery dtb
for legacy platforms), so set the dtb load offset in bootloader.
The dtb load address will be 'kernel_addr + FDT_OFFSET_TO_KERNEL'
(48MB memory reserved).

Test: Boots on imx8mq.

Change-Id: Ie597731992107ec2343e5ab6db0cab0e123f009c
Signed-off-by: Ji Luo <ji.luo@nxp.com>