util: avoid memory leak

Leak in pciGetVirtualFunctionIndex present since commit 17d64cab.

* src/util/pci.c: fix memory leak.
Signed-off-by: NAlex Jia <ajia@redhat.com>

src/util/pci.c

@@ -1965,6 +1965,7 @@ out:
     for (i = 0; i < num_virt_fns; i++)
          VIR_FREE(virt_fns[i]);
 
+    VIR_FREE(virt_fns);
     VIR_FREE(vf_bdf);
 
     return ret;