ARM: add Armada 1500-mini and Chromecast device tree files

This adds very basic device tree files for the Marvell Armada
1500-mini SoC (Berlin BG2CD) and the Google Chromecast. Currently,
SoC only has nodes for cpu, some clocks, l2 cache controller, local
timer, apb timers, uart, and interrupt controllers.
The Google Chromecast is a consumer device comprising the Armada
1500-mini SoC above.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>