ARM: am335x: Add support for chiliSOM

ARM: am335x: Add support for chiliSOM

chiliSOM is a System On Module (http://http://grinn-global.com/chilisom/).
It can't exists on its own, but will be used as part of other boards.

Hardware specification:
 * TI AM335x processor
 * 128M, 256M or 512M DDR3 memory
 * up to 256M NAND

We place source inside arch/arm/mach-omap2/ directory and make it
possible to reuse initialization code (i.e. DDR, NAND init) for all
boards that use it.

Signed-off-by: Marcin Niestroj <m.niestroj@grinn-global.com>
Reviewed-by: Tom Rini <trini@konsulko.com>