dts: Add support for Device Tree

This patch adds support for using device tree configuration files for
configuring ARM platforms.

In this patch, only the FLASH_SIZE, SRAM_SIZE, NUM_IRQS, and
NUM_IRQ_PRIO_BITS were removed from the Kconfig options.  A minimal set
of options were removed so that it would be easier to work through the
plumbing of the build system.

It should be noted that the host system must provide access to the
device tree compiler (DTC).  The DTC can usually be installed on host
systems through distribution packages or by downloading and compiling
from https://git.kernel.org/pub/scm/utils/dtc/dtc.git



This patch also requires the Python yaml package.

This change implements parts of each of the following Jira:
ZEP-1304
ZEP-1305
ZEP-1306
ZEP-1307
ZEP-1589

Change-Id: If1403801e19d9d85031401b55308935dadf8c9d8
Signed-off-by: Andy Gross <andy.gross@linaro.org>