cxgb4: Remove redundant NULL check

Fix the following coccicheck warnings:

./drivers/net/ethernet/chelsio/cxgb4/cudbg_lib.c:3540:2-8: WARNING: NULL
check before some freeing functions is not needed.
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/chelsio/cxgb4/cudbg_lib.c

@@ -3536,8 +3536,7 @@ int cudbg_collect_qdesc(struct cudbg_init *pdbg_init,
 	}
 
 out_free:
-	if (data)
-		kvfree(data);
+	kvfree(data);
 
 #undef QDESC_GET_FLQ
 #undef QDESC_GET_RXQ