ipv6: coding style: comparison for equality with NULL

The ipv6 code uses a mixture of coding styles. In some instances check for NULL
pointer is done as x == NULL and sometimes as !x. !x is preferred according to
checkpatch and this patch makes the code consistent by adopting the latter
form.

No changes detected by objdiff.

Signed-off-by: Ian Morris <ipm@chirality.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 58c0e6a..fe742fa 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1476,7 +1476,7 @@
 	int remaining;
 	u32 *mp;
 
-	if (cfg->fc_mx == NULL)
+	if (!cfg->fc_mx)
 		return 0;
 
 	mp = kzalloc(sizeof(u32) * RTAX_MAX, GFP_KERNEL);