Add the device tree files for sama5d4 Xplained board.
The dts files are copied from Linux-4.4, do the following changes.
- add reg property for pinctrl node.
- move the gpio nodes(pioA, pioB, pioC ...) from the pinctrl child's
nodes to its slibling nodes.
- 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 warnings.
Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
