Implements set_inject_error() with the low-level code needed to inject
memory errors at Nehalem, and adds some sysfs nodes to allow error injection

The next patch will add an API for error injection.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

This driver is meant to support i7 core/i7core extreme desktop
processors and Xeon 35xx/55xx series with integrated memory controller.
It is likely that it can be expanded in the future to work with other
processor series based at the same Memory Controller design.

For now, it has just a few MCH status reads.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>