[ARCH] Make DTS layout suitable for external DTB files

Currently, we only have built-in DTB compiled with Xvisor
binary but we also need to have scope of providing DTB file
externally via bootloader.

To achieve this, we must first have DTS layout similar to
Linux DTS layout so that bootloader such as u-boot and QEMU
can fixup DTB before passing it to Xvisor.

This patch does following changes to Xvisor DTS layout:
1. Rename /choosen to /chosen
2. Remove /host node and all child nodes of /host will
   be directly under / node
3. Use reg property in /memory node to inform Xvisor about
   available memory banks.

In simpler words, Xvisor DTS layout would be an extension of
Linux DTS layout. This means Xvisor DTS files will look very
similar to Linux DTS files except we will have /vmm, /guests,
and /templates nodes under / node which will not be present
in Linux DTS files.

Signed-off-by: Anup Patel <anup@brainfault.org>
[LIBS] libfdt: Fix libfdt_find_node_recursive()

Signed-off-by: Sukanto Ghosh <sukantoghosh@gmail.com>
Signed-off-by: Anup Patel <anup@brainfault.org>
[DOCS] Fix realview-pb-a8 test path in omap3-beagle doc

Signed-off-by: Sukanto Ghosh <sukantoghosh@gmail.com>
[TOP] Added dtbs target to Makefile for building external dtbs

To support bootloader provided DTB file, we need a mechanism for building
dtb files. This patch allows generating all possible DTBs for selected host
on running 'make dtbs'.

Signed-off-by: Sukanto Ghosh <sukantoghosh@gmail.com>
Merge branch 'x86-next', remote-tracking branch 'upstream/master' into x86-next
[x86] Have command line and memory size from multiboot.

Signed-off-by: Himanshu Chauhan <hschauhan@nulltrace.org>