[PPP]: remove redundant NULL pointer checks before kfree & vfree

kfree() and vfree() can both deal with NULL pointers. This patch removes 
redundant NULL pointer checks from the ppp code in drivers/net/

Signed-off-by: Jesper Juhl <juhl-lkml@dif.dk>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ppp_generic.c b/drivers/net/ppp_generic.c
index c456dc8..3b377f6 100644
--- a/drivers/net/ppp_generic.c
+++ b/drivers/net/ppp_generic.c
@@ -2467,14 +2467,10 @@
 	skb_queue_purge(&ppp->mrq);
 #endif /* CONFIG_PPP_MULTILINK */
 #ifdef CONFIG_PPP_FILTER
-	if (ppp->pass_filter) {
-		kfree(ppp->pass_filter);
-		ppp->pass_filter = NULL;
-	}
-	if (ppp->active_filter) {
-		kfree(ppp->active_filter);
-		ppp->active_filter = NULL;
-	}
+	kfree(ppp->pass_filter);
+	ppp->pass_filter = NULL;
+	kfree(ppp->active_filter);
+	ppp->active_filter = NULL;
 #endif /* CONFIG_PPP_FILTER */
 
 	kfree(ppp);