Add the device tree file for sama5d4ek board.
The dts file is copied from Linux-4.4, do the following changes.
- add the "u-boot,dm-pre-reloc" property to determine which nodes
which are needed by SPL and by the board_init_f stage.
- fix the compilation warning.
Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
