ARM: dts: am33xx: Add an empty chosen node to top level DTSI

Commit f8bf0161 ("ARM: dts: am33xx: Remove skeleton.dtsi usage")
removed the skeleton.dtsi usage since we want to get rid of it.

But this can cause issues when booting a kernel with a boot-loader
that doesn't create a chosen node if this isn't present in the DTB
since the decompressor relies on a pre-existing chosen node to be
available to insert the command line and merge other ATAGS info.

Fixes: f8bf0161 ("ARM: dts: am33xx: Remove skeleton.dtsi usage")
Reported-by: Pali Rohar <pali.rohar@gmail.com>
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/boot/dts/am33xx.dtsi

@@ -16,6 +16,7 @@ / {
 	interrupt-parent = <&intc>;
 	#address-cells = <1>;
 	#size-cells = <1>;
+	chosen { };
 
 	aliases {
 		i2c0 = &i2c0;