ARM: mx6: Change the FDT loading address to avoid overlaping

This patch fixes allow for the DeviceTree and initrd relocation fixing
the boot of FSL 3.10.9-1.0.0-alpha kernel.

This changes following boards:

 - wandboard
 - nitrogen6x
 - cgtqmx6eval

The reasoning, as explained by Hui Liu, is:

,----
| The FDT blob will be placed at DDR physical addr: 0x11000000. When Linux kernel
| Boot up, it will decompress the compressed kernel image and place the decompressed
| kernel image at the low end of the DDR memory and start running from it. If the
| decompressed kernel image is bigger for example than 16M, it may over written the
| fdt blob which u-boot loaded to the DDR memory @0x11000000 with fdt_addr=0x11000000
|
| To expand the fdt_addr from 0x11000000 to 0x18000000, which can avoid the override
| Since we will not likely have one kernel image larger than 128MB.
`----

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