flow.h/flow_keys.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/flow.h

@@ -215,12 +215,13 @@ typedef struct flow_cache_object *(*flow_resolve_t)(
 		struct net *net, const struct flowi *key, u16 family,
 		u8 dir, struct flow_cache_object *oldobj, void *ctx);
 
-extern struct flow_cache_object *flow_cache_lookup(
-		struct net *net, const struct flowi *key, u16 family,
-		u8 dir, flow_resolve_t resolver, void *ctx);
+struct flow_cache_object *flow_cache_lookup(struct net *net,
+					    const struct flowi *key, u16 family,
+					    u8 dir, flow_resolve_t resolver,
+					    void *ctx);
 
-extern void flow_cache_flush(void);
-extern void flow_cache_flush_deferred(void);
+void flow_cache_flush(void);
+void flow_cache_flush_deferred(void);
 extern atomic_t flow_cache_genid;
 
 #endif

include/net/flow_keys.h

@@ -13,5 +13,5 @@ struct flow_keys {
 	u8 ip_proto;
 };
 
-extern bool skb_flow_dissect(const struct sk_buff *skb, struct flow_keys *flow);
+bool skb_flow_dissect(const struct sk_buff *skb, struct flow_keys *flow);
 #endif