x-tools: initial support for armv7a tool chain

This patch adds initial support for an armv7a soft-float (no FPU)
toolchain using uclibc.

Verified by compiling a simple 'hello world' program and running under
qemu-arm.
armv7a: initial kernel configuration for ARM

Baseline kernel configuration for ARM platforms.
busybox-iorw: update iorw command for arm

Add armv7 assembly to the memory barriers used by the iorw command.
build system changes to support ARM platform

Adjust and refractor portions of the kernel and ONIE image build
process to accommodate the ARM platform.

For the most part the ARM platform is following the PowerPC model of
using U-Boot with a kernel, initramfs and dtb file.
qemu_armv7a: initial machine configuration

Initial support for ARMv7a based virtual machine.
arm: initial 3.2.x kernel configuration for ARM

This patch adds an initial kernel configuration for a 3.2.x kernel.

Defaults to following ARM_ARCH and PLATFORM:
  CONFIG_ARCH_VERSATILE=y
  CONFIG_ARCH_VERSATILE_PB=y
  CONFIG_MACH_VERSATILE_DT=y
  CONFIG_PLAT_VERSATILE_CLCD=y
  CONFIG_PLAT_VERSATILE_FPGA_IRQ=y
  CONFIG_PLAT_VERSATILE_SCHED_CLOCK=y
  CONFIG_PLAT_VERSATILE=y
  CONFIG_ARM_TIMER_SP804=y
armv7a_3_2: initial machine configuration

Initial commit of files to support the versatile-pb machine using the
3.2.x kernel series.

This patch set is not fully functional, but it is enough to build the
toolchain needed for 3.2.x kernel development.
rename powerpc-softfloat rootfs and installer files to u-boot-arch

The rootfs and installer files (including demo OS) for
powerpc-softfloat are generic enough to use on all known U-Boot based
systems, like ARM.

Making these scripts and files common allows both powerpc-softfloat
and armv7a platforms to use the same files.
onie-mk-bin.sh: add new format 'uboot_ubootenv-up'

This image format is a discontinuous image format for platforms that
locate the boot loader at 0x00000000.

This format emits two binaries:

1.  u-boot + u-boot-env in one binary: onie-<machine>.bin.uboot+env
2.  ONIE kernel+initramfs in another binary: onie-<machine>.bin

In increasing physical address space the order of u-boot+env is:

   low : u-boot
   high: u-boot env

This is in contract to the 'uboot_ubootenv' image format, which also
emits two binaries.  In that case the layout is:

   low : u-boot env
   high: u-boot
qemu_armv7a: update INSTALL instructions

Update the INSTALL instructions for the qemu_armv7a ONIE machine,
including:

- building and patching qemu-2.1.2
- creating disk and flash images
- setting the EEPROM contents
- launching VM using qemu