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>
diff --git a/drivers/net/usb/net1080.c b/drivers/net/usb/net1080.c
index 3202c19..861ff45 100644
--- a/drivers/net/usb/net1080.c
+++ b/drivers/net/usb/net1080.c
@@ -473,8 +473,8 @@ net1080_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
 
 	/* maybe pad; then trailer */
 	if (!((skb->len + sizeof *trailer) & 0x01))
-		*skb_put(skb, 1) = PAD_BYTE;
-	trailer = (struct nc_trailer *) skb_put(skb, sizeof *trailer);
+		*(u8 *)skb_put(skb, 1) = PAD_BYTE;
+	trailer = skb_put(skb, sizeof *trailer);
 	put_unaligned(header->packet_id, &trailer->packet_id);
 #if 0
 	netdev_dbg(dev->net, "frame >tx h %d p %d id %d\n",