ARM: tegra: add Acer Chromebook 13 device tree

The Acer Chromebook 13, codenamed Big, contains an NVIDIA tegra124
processor and is similar to the Venice2 reference platform.

The keyboard, USB 2, audio, sdcard and emmc have been tested
and work on the 1366x768 models. The Full HD models haven't been
tested yet.

WiFi does not yet work, it needs at least some PMIC changes to enable
the 32k clock.

The elan trackpad is not yet functional but hopefully will be soon as
there are patches under review.

There is also an issue on reboot because the TPM isn't reset.  It will
cause the stock firmware to enter recovery mode.  This can be worked
around by an EC-reset, press the refresh and power keys at the same
time.

Signed-off-by: Dylan Reid <dgreid@chromium.org>
Signed-off-by: Stephen Warren <swarren@nvidia.com>