omap2: modify omap24xx.h to improve constant names and prepare for multi-arch kernels

Redo the defines in omap24xx.h to fix poorly-named defines, such as
OMAP24XX_SDRC_BASE, which is different between 2420 and 2430.  Also,
prepare for future multi-architecture kernels by removing the
architecture prefixes from several of the defines.  (Presumably in the
future these will be assigned to 'static void __iomem *'s by runtime
init code depending on the CPU type.)

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>