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>
diff --git a/drivers/isdn/i4l/isdn_bsdcomp.c b/drivers/isdn/i4l/isdn_bsdcomp.c
index 6ade091..3035210 100644
--- a/drivers/isdn/i4l/isdn_bsdcomp.c
+++ b/drivers/isdn/i4l/isdn_bsdcomp.c
@@ -602,7 +602,8 @@ static int bsd_compress(void *state, struct sk_buff *skb_in, struct sk_buff *skb
 	 * Do not emit a completely useless byte of ones.
 	 */
 	if (bitno < 32 && skb_out && skb_tailroom(skb_out) > 0)
-		*(u8 *)skb_put(skb_out, 1) = (unsigned char)((accm | (0xff << (bitno - 8))) >> 24);
+		skb_put_u8(skb_out,
+			   (unsigned char)((accm | (0xff << (bitno - 8))) >> 24));
 
 	/*
 	 * Increase code size if we would have without the packet
@@ -698,7 +699,7 @@ static int bsd_decompress(void *state, struct sk_buff *skb_in, struct sk_buff *s
 	db->bytes_out += ilen;
 
 	if (skb_tailroom(skb_out) > 0)
-		*(u8 *)skb_put(skb_out, 1) = 0;
+		skb_put_u8(skb_out, 0);
 	else
 		return DECOMP_ERR_NOMEM;
 
@@ -816,7 +817,7 @@ static int bsd_decompress(void *state, struct sk_buff *skb_in, struct sk_buff *s
 #endif
 
 		if (extra)		/* the KwKwK case again */
-			*(u8 *)skb_put(skb_out, 1) = finchar;
+			skb_put_u8(skb_out, finchar);
 
 		/*
 		 * If not first code in a packet, and