x86: remove rdc321x_defs.h

This file is replaced by a cleaner version with the adding of a MFD driver for
the southbridge.

Signed-off-by: Florian Fainelli <florian@openwrt.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>