wifi: iwlwifi: fw: move memset before early return

Clang static analysis reports this representative issue
dbg.c:1455:6: warning: Branch condition evaluates to
a garbage value
  if (!rxf_data.size)
       ^~~~~~~~~~~~~~

This check depends on iwl_ini_get_rxf_data() to clear
rxf_data but the function can return early without
doing the clear.  So move the memset before the early
return.

Fixes: cc9b6012 ("iwlwifi: yoyo: use hweight_long instead of bit manipulating")
Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230414130637.872a7175f1ff.I33802a77a91998276992b088fbe25f61c87c33ac@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/intel/iwlwifi/fw/dbg.c

@@ -1388,13 +1388,13 @@ static void iwl_ini_get_rxf_data(struct iwl_fw_runtime *fwrt,
 	if (!data)
 		return;
 
+	memset(data, 0, sizeof(*data));
+
 	/* make sure only one bit is set in only one fid */
 	if (WARN_ONCE(hweight_long(fid1) + hweight_long(fid2) != 1,
 		      "fid1=%x, fid2=%x\n", fid1, fid2))
 		return;
 
-	memset(data, 0, sizeof(*data));
-
 	if (fid1) {
 		fifo_idx = ffs(fid1) - 1;
 		if (WARN_ONCE(fifo_idx >= MAX_NUM_LMAC, "fifo_idx=%d\n",