ARM: OMAP: Remove plat/io.h by splitting it into mach/io.h and mach/hardware.h

This is needed to minimize io.h so the SoC specific io.h
for ARMs can removed.

Note that minimal driver changes for DSS and RNG are needed to
include cpu.h for SoC detection macros.

Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Tony Lindgren <tony@atomide.com>