l2tp: prefer using BIT macro

Use BIT(x) rather than (1<<x), reported by checkpatch.pl.
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/l2tp/l2tp_core.h

@@ -21,11 +21,11 @@
 
 /* Per tunnel, session hash table size */
 #define L2TP_HASH_BITS	4
-#define L2TP_HASH_SIZE	(1 << L2TP_HASH_BITS)
+#define L2TP_HASH_SIZE	BIT(L2TP_HASH_BITS)
 
 /* System-wide, session hash table size */
 #define L2TP_HASH_BITS_2	8
-#define L2TP_HASH_SIZE_2	(1 << L2TP_HASH_BITS_2)
+#define L2TP_HASH_SIZE_2	BIT(L2TP_HASH_BITS_2)
 
 struct sk_buff;