busy_poll: cleanup do-nothing placeholders

When renaming ll_poll to busy poll, I introduced a typo
in the name of the do-nothing placeholder for sk_busy_loop
and called it sk_busy_poll.
This broke compile when busy poll was not configured.
Cong Wang submitted a patch to fixed that.
This patch removes the now redundant, misspelled placeholder.
Signed-off-by: NEliezer Tamir <eliezer.tamir@linux.intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/busy_poll.h

@@ -162,11 +162,6 @@ static inline bool sk_can_busy_loop(struct sock *sk)
 	return false;
 }
 
-static inline bool sk_busy_poll(struct sock *sk, int nonblock)
-{
-	return false;
-}
-
 static inline void skb_mark_napi_id(struct sk_buff *skb,
 				    struct napi_struct *napi)
 {