Interrupt storm on acpi0 occurred after madt.c change

[Nate Lawson]

It should work fine in Linux.  mp_config_ioapic_for_sci() in
arch/i386/kernel/mpparse.c has an exception for Tyans:

/*
 * Although the ACPI spec says that the SCI should be level/low
 * don't reprogram it unless there is an explicit MADT OVR entry
 * instructing us to do so -- otherwise we break Tyan boards which
 * have the SCI wired edge/high but no MADT OVR.
 */

This is for the case where there is no source override in the MADT for the
interrupt defined as ACPI_FADT->sci_int.

-Nate