OvmfPkg: IndustryStandard: factor out Virtio095.h

OvmfPkg: IndustryStandard: factor out Virtio095.h

In the upcoming virtio-1.0 series, we'll introduce "Virtio10.h". However,
the "Virtio.h" header file should continue to expose the generic type and
macro definitions for all virtio versions that OvmfPkg supports. Therefore
extract "Virtio095.h" like this:

  Virtio.h -> Virtio095.h

so that in the upcoming patches, we can insert "Virtio10.h" in the middle
of the inclusion chain.

This follows the example of "Acpi.h" and "Pci.h" under
"MdePkg/Include/IndustryStandard".

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Suggested-by: Jordan Justen <jordan.l.justen@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>