arm/dts: Add support for OMAP3 Beagle board

Add OMAP3 beagleboard DTS file to use the omap3.dtsi SoC file.

Add a default bootargs line to allow a boot from RAMDISK.

Add memory node information.

Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Cc: G, Manjunath Kondaiah <manjugk@ti.com>