OMAP7XX: Create omap7xx.h

This patch is part of a series which removes references to omap730 in code
which is shared with omap850, replacing them with references to omap7xx.

This include file is intended to replace omap730.h and omap850.h
All values defined herein are identical to those in both the old files.

Signed-off-by: Alistair Buxton <a.j.buxton@gmail.com>
Reviewed-by: Zebediah C. McClure <zmc@lurian.net>