[NET]: Fix alloc_skb comment typo

Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -1081,7 +1081,7 @@ static inline void __skb_queue_purge(struct sk_buff_head *list)
  *	the headroom they think they need without accounting for the
  *	built in space. The built in space is used for optimisations.
  *
- *	%NULL is returned in there is no free memory.
+ *	%NULL is returned if there is no free memory.
  */
 static inline struct sk_buff *__dev_alloc_skb(unsigned int length,
 					      gfp_t gfp_mask)
@@ -1101,7 +1101,7 @@ static inline struct sk_buff *__dev_alloc_skb(unsigned int length,
  *	the headroom they think they need without accounting for the
  *	built in space. The built in space is used for optimisations.
  *
- *	%NULL is returned in there is no free memory. Although this function
+ *	%NULL is returned if there is no free memory. Although this function
  *	allocates memory it can be called from an interrupt.
  */
 static inline struct sk_buff *dev_alloc_skb(unsigned int length)