be2net: fix vfs enumeration

Current VFs enumeration algorithm used in be_find_vfs does not take domain
number into the match. The match found in igb/ixgbe is more elegant and
safe.

This 2nd version uses pci_physfn instead of checking dev->physfn directly.

Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>