arm: dts: ti_lm3s6965: Add Device Tree Support

Introduce a simple device tree for the TI lm3s6965 SoC and QEMU
Cortex-M3 board port.  We get flash and memory base addresses and sizes
from the device tree as well as the ARM NVIC number of priority bits.

Change-Id: I4452b5543de7be55518997e54837ccbfd4f121df
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>