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.

Signed-off-by: Curt Brune <curt@cumulusnetworks.com>
armv4a: 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.