networking: add and use skb_put_u8()

Joe and Bjørn suggested that it'd be nicer to not have the
cast in the fairly common case of doing
	*(u8 *)skb_put(skb, 1) = c;

Add skb_put_u8() for this case, and use it across the code,
using the following spatch:

    @@
    expression SKB, C, S;
    typedef u8;
    identifier fn = {skb_put};
    fresh identifier fn2 = fn ## "_u8";
    @@
    - *(u8 *)fn(SKB, S) = C;
    + fn2(SKB, C);

Note that due to the "S", the spatch isn't perfect, it should
have checked that S is 1, but there's also places that use a
sizeof expression like sizeof(var) or sizeof(u8) etc. Turns
out that nobody ever did something like
	*(u8 *)skb_put(skb, 2) = c;

which would be wrong anyway since the second byte wouldn't be
initialized.

Suggested-by: Joe Perches <joe@perches.com>
Suggested-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/bluetooth/dtl1_cs.c

@@ -226,7 +226,7 @@ static void dtl1_receive(struct dtl1_info *info)
 			}
 		}
 
-		*(u8 *)skb_put(info->rx_skb, 1) = inb(iobase + UART_RX);
+		skb_put_u8(info->rx_skb, inb(iobase + UART_RX));
 		nsh = (struct nsh *)info->rx_skb->data;
 
 		info->rx_count--;
@@ -414,7 +414,7 @@ static int dtl1_hci_send_frame(struct hci_dev *hdev, struct sk_buff *skb)
 	skb_reserve(s, NSHL);
 	skb_copy_from_linear_data(skb, skb_put(s, skb->len), skb->len);
 	if (skb->len & 0x0001)
-		*(u8 *)skb_put(s, 1) = 0;	/* PAD */
+		skb_put_u8(s, 0);	/* PAD */
 
 	/* Prepend skb with Nokia frame header and queue */
 	memcpy(skb_push(s, NSHL), &nsh, NSHL);