xen/pt: Emulate multifunction bit in header type

xen/pt: Emulate multifunction bit in header type

The intention of the code appears to have been to unconditionally set
the multifunction bit but since the emulation mask is 0x00 it has no
effect. Instead, emulate the bit and set it based on the multifunction
property of the PCIDevice (which can be set using QAPI).

This allows making passthrough devices appear as functions in a Xen
guest.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Reviewed-by: Paul Durrant <paul@xen.org>
Message-Id: <20231103172601.1319375-1-ross.lagerwall@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>