IBM Real-Time "SMI Free" mode driver -v7

IBM Real-Time "SMI Free" mode driver -v7

After a period of RFC for this driver, I think it is ready
for inclusion in the platform-driver-x86 tree, hopefully to
be staged in the next merge window into Linus's tree.

--Vernon

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IBM Real-Time "SMI Free" mode driver

This driver supports the Real-Time Linux (RTL) BIOS feature.
The RTL feature allows non-fatal System Management Interrupts
(SMIs) to be disabled on supported IBM platforms and is
intended to be coupled with a user-space daemon to monitor
the hardware in a way that can be prioritized and scheduled
to better suit the requirements for the system.

The Device is presented as a special "_RTL_" table to the OS
in the Extended BIOS Data Area.  There is a simple protocol
for entering and exiting the mode at runtime.  This driver
creates a simple sysfs interface to allow a simple entry and
exit from RTL mode in the UFI/BIOS.

Since the driver is specific to IBM SystemX hardware (x86-
based servers) it only builds on x86 builds.  To reduce the
risk of loading on the wrong hardware, the module uses DMI
information and checks a list of servers that are known to
work.

Signed-off-by: Vernon Mauery <vernux@us.ibm.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>