net: llc: Correct function name llc_pdu_set_pf_bit() in header

Fix the following make W=1 kernel build warning:

 net/llc/llc_pdu.c:36: warning: expecting prototype for pdu_set_pf_bit(). Prototype was for llc_pdu_set_pf_bit() instead
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/llc/llc_pdu.c

@@ -24,7 +24,7 @@ void llc_pdu_set_cmd_rsp(struct sk_buff *skb, u8 pdu_type)
 }
 
 /**
- *	pdu_set_pf_bit - sets poll/final bit in LLC header
+ *	llc_pdu_set_pf_bit - sets poll/final bit in LLC header
  *	@skb: Frame to set bit in
  *	@bit_value: poll/final bit (0 or 1).
  *