x86: work around certain Intel BIOSes causing (transient) hangs during boot

x86: work around certain Intel BIOSes causing (transient) hangs during boot

They apparently leave the USB legacy emulation bits set in ICH10's
SMI Control and Enable register, but fail to handle the resulting SMIs
gracefully. The hangs can apparently extend indefinitely, but are
commonly observed to last between a few seconds and a minute.

This assumes that only ICH10-based systems on Intel main boards with
Intel BIOS may be affected. Until Intel comes up with a more precise
identification of affected BIOSes, all Intel ones on Intel boards
will get this workaround applied.

Signed-off-by: Jan Beulich <jbeulich@novell.com>