arm: Introduce arch/arm/mach-omap2 for OMAP2 derivative platforms

This moves what was in arch/arm/cpu/armv7/omap-common in to
arch/arm/mach-omap2 and moves
arch/arm/cpu/armv7/{am33xx,omap3,omap4,omap5} in to arch/arm/mach-omap2
as subdirectories.  All refernces to the former locations are updated to
the current locations.  For the logic to decide what our outputs are,
consolidate the tests into a single config.mk rather than including 4.

Signed-off-by: Tom Rini <trini@konsulko.com>