arcnet: Remove pointer comparisons to NULL

Use direct tests of pointer instead.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
diff --git a/drivers/net/arcnet/arc-rawmode.c b/drivers/net/arcnet/arc-rawmode.c
index 7fc5b042..40035ee 100644
--- a/drivers/net/arcnet/arc-rawmode.c
+++ b/drivers/net/arcnet/arc-rawmode.c
@@ -97,7 +97,7 @@
 		ofs = 256 - length;
 
 	skb = alloc_skb(length + ARC_HDR_SIZE, GFP_ATOMIC);
-	if (skb == NULL) {
+	if (!skb) {
 		dev->stats.rx_dropped++;
 		return;
 	}