dts: move device tree sources to arch/$(ARCH)/dts/

Unlike Linux Kernel, U-Boot historically had *.dts files under
board/$(VENDOR)/dts/ and *.dtsi files under arch/$(ARCH)/dts/.

I think arch/$(ARCH)/dts dicretory is a better location
to store both *.dts and *.dtsi files.

For example, before this commit, board/xilinx/dts directory
had both Microblaze dts (microblaze-generic.dts) and
ARM dts (zynq-*.dts), which are totally unrelated.

This commit moves *.dts to arch/$(ARCH)/dts/ directories,
allowing us to describe nicely mutiple DTBs generation in the next commit.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>

board/compulab/dts/tegra20-trimslice.dts

@@ -1,64 +0,0 @@
-/dts-v1/;
-
-#include "tegra20.dtsi"
-
-/ {
-	model = "Compulab TrimSlice board";
-	compatible = "compulab,trimslice", "nvidia,tegra20";
-
-	aliases {
-		usb0 = "/usb@c5008000";
-		usb1 = "/usb@c5000000";
-		sdhci0 = "/sdhci@c8000600";
-		sdhci1 = "/sdhci@c8000000";
-	};
-
-	memory {
-		reg = <0x00000000 0x40000000>;
-	};
-
-	serial@70006000 {
-		clock-frequency = <216000000>;
-	};
-
-	i2c@7000c000 {
-		status = "disabled";
-	};
-
-	spi@7000c380 {
-		status = "okay";
-		spi-max-frequency = <25000000>;
-	};
-
-	i2c@7000c400 {
-		status = "disabled";
-	};
-
-	i2c@7000c500 {
-		status = "disabled";
-	};
-
-	i2c@7000d000 {
-		status = "disabled";
-	};
-
-	usb@c5000000 {
-		nvidia,vbus-gpio = <&gpio 170 0>; /* PV2 */
-	};
-
-	usb@c5004000 {
-		status = "disabled";
-	};
-
-	sdhci@c8000000 {
-		status = "okay";
-		bus-width = <4>;
-	};
-
-	sdhci@c8000600 {
-		status = "okay";
-		cd-gpios = <&gpio 121 1>; /* gpio PP1 */
-		wp-gpios = <&gpio 122 0>; /* gpio PP2 */
-		bus-width = <4>;
-	};
-};