ARM: dts: at91: add dts files for sama5d4 Xplained

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>
diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
index c131149..a6f947c 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -358,6 +358,9 @@
 dtb-$(CONFIG_TARGET_SAMA5D3_XPLAINED) += \
 	at91-sama5d3_xplained.dtb
 
+dtb-$(CONFIG_TARGET_SAMA5D4_XPLAINED) += \
+	at91-sama5d4_xplained.dtb
+
 dtb-$(CONFIG_ARCH_BCM283X) += \
 	bcm2835-rpi-a-plus.dtb \
 	bcm2835-rpi-a.dtb \