networking: make skb_pull & friends return void pointers

It seems like a historic accident that these return unsigned char *,
and in many places that means casts are required, more often than not.

Make these functions return void * and remove all the casts across
the tree, adding a (u8 *) cast only where the unsigned char pointer
was used directly, all done with the following spatch:

    @@
    expression SKB, LEN;
    typedef u8;
    identifier fn = {
            skb_pull,
            __skb_pull,
            skb_pull_inline,
            __pskb_pull_tail,
            __pskb_pull,
            pskb_pull
    };
    @@
    - *(fn(SKB, LEN))
    + *(u8 *)fn(SKB, LEN)

    @@
    expression E, SKB, LEN;
    identifier fn = {
            skb_pull,
            __skb_pull,
            skb_pull_inline,
            __pskb_pull_tail,
            __pskb_pull,
            pskb_pull
    };
    type T;
    @@
    - E = ((T *)(fn(SKB, LEN)))
    + E = fn(SKB, LEN)

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 454ea37..ac9d10d 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1931,22 +1931,22 @@ static inline unsigned char *__skb_push(struct sk_buff *skb, unsigned int len)
 	return skb->data;
 }
 
-unsigned char *skb_pull(struct sk_buff *skb, unsigned int len);
-static inline unsigned char *__skb_pull(struct sk_buff *skb, unsigned int len)
+void *skb_pull(struct sk_buff *skb, unsigned int len);
+static inline void *__skb_pull(struct sk_buff *skb, unsigned int len)
 {
 	skb->len -= len;
 	BUG_ON(skb->len < skb->data_len);
 	return skb->data += len;
 }
 
-static inline unsigned char *skb_pull_inline(struct sk_buff *skb, unsigned int len)
+static inline void *skb_pull_inline(struct sk_buff *skb, unsigned int len)
 {
 	return unlikely(len > skb->len) ? NULL : __skb_pull(skb, len);
 }
 
-unsigned char *__pskb_pull_tail(struct sk_buff *skb, int delta);
+void *__pskb_pull_tail(struct sk_buff *skb, int delta);
 
-static inline unsigned char *__pskb_pull(struct sk_buff *skb, unsigned int len)
+static inline void *__pskb_pull(struct sk_buff *skb, unsigned int len)
 {
 	if (len > skb_headlen(skb) &&
 	    !__pskb_pull_tail(skb, len - skb_headlen(skb)))
@@ -1955,7 +1955,7 @@ static inline unsigned char *__pskb_pull(struct sk_buff *skb, unsigned int len)
 	return skb->data += len;
 }
 
-static inline unsigned char *pskb_pull(struct sk_buff *skb, unsigned int len)
+static inline void *pskb_pull(struct sk_buff *skb, unsigned int len)
 {
 	return unlikely(len > skb->len) ? NULL : __pskb_pull(skb, len);
 }
@@ -2938,7 +2938,7 @@ static inline void skb_postpush_rcsum(struct sk_buff *skb,
 	__skb_postpush_rcsum(skb, start, len, 0);
 }
 
-unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len);
+void *skb_pull_rcsum(struct sk_buff *skb, unsigned int len);
 
 /**
  *	skb_push_rcsum - push skb and update receive checksum