networking: make skb_put & 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 (skb_put, __skb_put and pskb_put) 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_put, __skb_put };
    @@
    - *(fn(SKB, LEN))
    + *(u8 *)fn(SKB, LEN)

    @@
    expression E, SKB, LEN;
    identifier fn = { skb_put, __skb_put };
    type T;
    @@
    - E = ((T *)(fn(SKB, LEN)))
    + E = fn(SKB, LEN)

which actually doesn't cover pskb_put since there are only three
users overall.

A handful of stragglers were converted manually, notably a macro in
drivers/isdn/i4l/isdn_bsdcomp.c and, oddly enough, one of the many
instances in net/bluetooth/hci_sock.c. In the former file, I also
had to fix one whitespace problem spatch introduced.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wireless/intel/ipw2x00/ipw2200.c

@@ -10371,7 +10371,7 @@ static void ipw_handle_promiscuous_tx(struct ipw_priv *priv,
 		if (!dst)
 			continue;
 
-		rt_hdr = (void *)skb_put(dst, sizeof(*rt_hdr));
+		rt_hdr = skb_put(dst, sizeof(*rt_hdr));
 
 		rt_hdr->it_version = PKTHDR_RADIOTAP_VERSION;
 		rt_hdr->it_pad = 0;

drivers/net/wireless/intel/ipw2x00/libipw_tx.c

@@ -439,8 +439,7 @@ netdev_tx_t libipw_xmit(struct sk_buff *skb, struct net_device *dev)
 
 	if (rts_required) {
 		skb_frag = txb->fragments[0];
-		frag_hdr =
-		    (struct libipw_hdr_3addrqos *)skb_put(skb_frag, hdr_len);
+		frag_hdr = skb_put(skb_frag, hdr_len);
 
 		/*
 		 * Set header frame_ctl to the RTS.