net: sunhme: Fix uninitialized return code

Fix an uninitialized return code if we never found a qfe slot. It would be
a bug if we ever got into this situation, but it's good to return something
tracable.

Fixes: acb3f35f ("sunhme: forward the error code from pci_enable_device()")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Sean Anderson <seanga2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>