intr-remap: generic support for remapping HPET MSIs

Generic support for remapping HPET MSI's by parsing the HPET timer block
device scope in the ACPI DRHD tables. This is needed for platforms
supporting interrupt-remapping and MSI capable HPET timer block.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Jay Fenlason <fenlason@redhat.com>
LKML-Reference: <20090804190729.477649000@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>