mx6sl: Adjust fdt_addr to avoid address overlapping

Similarly as it was done on commit 6584a1b5 (ARM: mx6: Change the FDT loading
address to avoid overlaping), we need to adjust the fdt_addr in order to be
able to boot FSL 3.10 kernel.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Otavio Salvador <otavio@ossystems.com.br>