jailhouse: Provide detection for non-x86 systems

Implement jailhouse_paravirt() via device tree probing on architectures
!= x86. Will be used by the PCI core.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Cc: jailhouse-dev@googlegroups.com
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-pci@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lkml.kernel.org/r/dae9fe0c6e63141c28ca90492fa5712b4c33ffb5.1520408357.git.jan.kiszka@siemens.com