common: board: Dont relocate FDT incase of CONFIG_OF_EMBED

Don't relocate fdt in case of CONFIG_OF EMBED as the fdt is
already embedded with u-boot image.
Update fdt_blob after relocation as the fdt will be copied
during u-boot relocation.

Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Alexey Brodkin <abrodkin@synopsys.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com> (QEMU x86)
Tested-by: Thomas Chou <thomas@wytron.com.tw> (Nios2)
Acked-by: Thomas Chou <thomas@wytron.com.tw>
Acked-by: Simon Glass <sjg@chromium.org>