If we don't have space for all the bus numbers required to enable VFs,
print the largest bus number required and the range available.

No functional change; improved error message only.
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Acked-by: NWei Yang <weiyang@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>