ARM: dts: am335x: Add DTS for ChiliSOM module

Since this is a SOM (System on Module) that will be part
of another embedded board (and can't really exist on its own)
define it as a "dtsi" that will be included in the Device tree
describing the whole system later on.

Hardware specification:
* AM335x SoC
* up to 512 MB RAM
* NAND Flash (8x interface, cs0)
* UART0
* PMIC
* I2C0 (for PMIC)
* 1x Ethernet MAC

Signed-off-by: Rostislav Lisovy <lisovy@jablotron.cz>
[tony@atomide.com: updated nand io size to be just 4]
Signed-off-by: Tony Lindgren <tony@atomide.com>