esp.h: Remove extern from function prototypes

There are a mix of function prototypes with and without extern
in the kernel sources.  Standardize on not using extern for
function prototypes.

Function prototypes don't need to be written with extern.
extern is assumed by the compiler.  Its use is as unnecessary as
using auto to declare automatic/local variables in a block.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/esp.h

@@ -13,7 +13,7 @@ struct esp_data {
 	struct crypto_aead *aead;
 };
 
-extern void *pskb_put(struct sk_buff *skb, struct sk_buff *tail, int len);
+void *pskb_put(struct sk_buff *skb, struct sk_buff *tail, int len);
 
 struct ip_esp_hdr;