omap: AM3517/05: Add craneboard support

Craneboard is a hardware development platform based on the
Sitara AM3517 ARM Cortex - A8 microprocessor device. This is a
low cost reference design.

This patch adds basic board file. Detailed support will follow in
subsequent patches.

  [1] http://www.ti.com/arm
  [2] http://www.mistralsolutions.com/products/craneboard.php

Signed-off-by: Srinath <srinath@mistralsolutions.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>