ARM: dts: at91: Add dts files for at91sam9260ek/9g20ek

The device tree source files of at91sam9g20ek and at91sam9260ek
boards are copied from the Linux v4.10, do the changes below.
 - Fix the build error for the usb0 node.
 - Add the reg property for the pinctrl node.
 - Move the gpio (pioA, pioB, pioC ...) nodes as the pinctrl's
   slibling nodes, instead of the child nodes.
 - Add the "u-boot,dm-pre-reloc" property for the dbgu node are used
   in board_init_f stage.
 - Add the clk pinctrl of the mmc0 node.
 - Fix the compilation warnings.

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
index 129e341..5a22fd3 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -352,6 +352,11 @@
 	keystone-k2e-evm.dtb \
 	keystone-k2g-evm.dtb
 
+dtb-$(CONFIG_TARGET_AT91SAM9260EK) += \
+	at91sam9260ek.dtb	\
+	at91sam9g20ek.dtb	\
+	at91sam9g20ek_2mmc.dtb
+
 dtb-$(CONFIG_TARGET_AT91SAM9M10G45EK) += at91sam9m10g45ek.dtb
 
 dtb-$(CONFIG_TARGET_AT91SAM9X5EK) += \