cxgb4: add common api support for configuring filters

Hello Rahul Lakkireddy,

The patch 578b46b9383c: "cxgb4: add common api support for configuring filters" from Sep 20, 2016, leads to the following static checker warning:

	drivers/net/ethernet/chelsio/cxgb4/cxgb4_filter.c:537 __cxgb4_set_filter()
	warn: we tested 'f->valid' before and it was 'false'

drivers/net/ethernet/chelsio/cxgb4/cxgb4_filter.c
512 /* Check to make sure that provided filter index is not
513 * already in use by someone else
514 */
515 f = &adapter->tids.ftid_tab[filter_id];
516 if (f->valid)
517 return -EBUSY;

If valid is set, then we return -EBUSY.

518
519 fidx = filter_id + adapter->tids.ftid_base;
520 ret = cxgb4_set_ftid(&adapter->tids, filter_id,
521 fs->type ? PF_INET6 : PF_INET);
522 if (ret)
523 return ret;
524

   525          /* Check to make sure the filter requested is writable ... */
   526          ret = writable_filter(f);
   527          if (ret) {

528 /* Clear the bits we have set above */
529 cxgb4_clear_ftid(&adapter->tids, filter_id,
530 fs->type ? PF_INET6 : PF_INET);
531 return ret;
532 }
533
534 /* Clear out any old resources being used by the filter before
535 * we start constructing the new filter.
536 */
537 if (f->valid)
538 clear_filter(adapter, f);

So probably these lines can be removed?

539
540 /* Convert the filter specification into our internal format.

   541           * We copy the PF/VF specification into the Outer VLAN field
   542           * here so the rest of the code -- including the interface to
   543           * the firmware -- doesn't have to constantly do these checks.
   544           */

regards,
dan carpenter