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/net/qrtr/qrtr.c b/net/qrtr/qrtr.c
index cff6791..5586609 100644
--- a/net/qrtr/qrtr.c
+++ b/net/qrtr/qrtr.c
@@ -259,7 +259,7 @@
 		return NULL;
 	skb_reset_transport_header(skb);
 
-	hdr = (struct qrtr_hdr *)skb_put(skb, QRTR_HDR_SIZE);
+	hdr = skb_put(skb, QRTR_HDR_SIZE);
 	hdr->version = cpu_to_le32(QRTR_PROTO_VER);
 	hdr->type = cpu_to_le32(type);
 	hdr->src_node_id = cpu_to_le32(src_node);