Pull xen bug fixes from David Vrabel:
- fix a PV regression in 3.19.
- fix a dom0 crash on hosts with large numbers of PIRQs.
- prevent pcifront from disabling memory or I/O port access, which may
trigger host crashes.
* tag 'stable/for-linus-4.0-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
xen-pciback: limit guest control of command register
xen/events: avoid NULL pointer dereference in dom0 on large machines
xen: Remove trailing semicolon from xenbus_register_frontend() definition
x86/xen: correct bug in p2m list initialization