GenWQE: Check pci_get_totalvfs return code

Currently the driver is using the pci_get_totalvfs() return code
directly in a loop. To avoid problems with potentially negative
returns in case of errors, we are adding some more sanity checking
code.

Signed-off-by: Frank Haverkamp <haver@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>