ARM: dts: at91: Add dts files for at91sam9n12ek

The device tree source files of at91sam9n12ek boards are copied from
the Linux v4.10, do the changes as below.
 - Add the reg property for the pinctrl node.
 - Move the gpio (pioA, pioB, pioC, pioD) nodes as the pinctrl's
   slibling nodes, instead of the child nodes.
 - Change the compatible of the spi flash to "spi-flash".
 - Add the spi0 aliases.
 - Fix the pinctrl-names of mmc0 node.
 - Add the "u-boot,dm-pre-reloc" property to determine which nodes
   are used by the board_init_f stage.
 - 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 092d2aa..2417f1f 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -359,6 +359,8 @@
 	at91sam9x25ek.dtb	\
 	at91sam9x35ek.dtb
 
+dtb-$(CONFIG_TARGET_AT91SAM9N12EK) += at91sam9n12ek.dtb
+
 dtb-$(CONFIG_TARGET_SAMA5D2_XPLAINED) += \
 	at91-sama5d2_xplained.dtb