x86: Add Dell OptiPlex 760 reboot quirk

Dell OptiPlex 760 hangs on reboot unless reboot=bios is used.  Add quirk
to reboot through the BIOS.

BugLink: https://bugs.launchpad.net/bugs/488319



Signed-off-by: Leann Ogasawara <leann.ogasawara@canonical.com>
LKML-Reference: <1264634958.27335.1091.camel@emiko>
Cc: <stable@kernel.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>