xen_platform: SUSE xenlinux unplug for emulated PCI

xen_platform: SUSE xenlinux unplug for emulated PCI

Implement SUSE specific unplug protocol for emulated PCI devices
in PVonHVM guests. Its a simple 'outl(1, (ioaddr + 4));'.
This protocol was implemented and used since Xen 3.0.4.
It is used in all SUSE/SLES/openSUSE releases up to SLES11SP3 and
openSUSE 12.3.
In addition old (pre-2011) VMDP versions are handled as well.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>