mlx4_core: Pass an invalid PCI id number to VFs

Currently, VFs have 0 in their dev->caps.function field.  This is a
valid pci id (usually of the PF).  Instead, pass an invalid PCI id to
the VF via QUERY_FW, so that if the value gets accessed in the VF
driver, we'll catch the problem.

Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Roland Dreier <roland@purestorage.com>