[PPP]: Sparse warning fixes.

Fix a bunch of warnings in PPP and related drivers. Mostly because
sparse doesn't like it when the the function is only marked private in
the forward declaration.

Signed-off-by: Stephen Hemminger <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ppp_deflate.c

···
  *	Returns the length of the compressed packet, or 0 if the
  *	packet is incompressible.
  */
-int z_compress(void *arg, unsigned char *rptr, unsigned char *obuf,
+static int z_compress(void *arg, unsigned char *rptr, unsigned char *obuf,
 	       int isize, int osize)
 {
 	struct ppp_deflate_state *state = (struct ppp_deflate_state *) arg;
···
  * bug, so we return DECOMP_FATALERROR for them in order to turn off
  * compression, even though they are detected by inspecting the input.
  */
-int z_decompress(void *arg, unsigned char *ibuf, int isize,
+static int z_decompress(void *arg, unsigned char *ibuf, int isize,
 		 unsigned char *obuf, int osize)
 {
 	struct ppp_deflate_state *state = (struct ppp_deflate_state *) arg;

drivers/net/ppp_generic.c

···
  * complete packet, or we get to the sequence number for a fragment
  * which hasn't arrived but might still do so.
  */
-struct sk_buff *
+static struct sk_buff *
 ppp_mp_reconstruct(struct ppp *ppp)
 {
 	u32 seq = ppp->nextseq;

drivers/net/ppp_synctty.c

···
  * Procedures for encapsulation and framing.
  */
 
-struct sk_buff*
+static struct sk_buff*
 ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *skb)
 {
 	int proto;

drivers/net/pppoe.c

···
 }
 
 static void *pppoe_seq_start(struct seq_file *seq, loff_t *pos)
+	__acquires(pppoe_hash_lock)
 {
 	loff_t l = *pos;
 
···
 }
 
 static void pppoe_seq_stop(struct seq_file *seq, void *v)
+	__releases(pppoe_hash_lock)
 {
 	read_unlock_bh(&pppoe_hash_lock);
 }

drivers/net/slhc.c

···
 
 
 /* Encode a number */
-unsigned char *
+static unsigned char *
 encode(unsigned char *cp, unsigned short n)
 {
 	if(n >= 256 || n == 0){
···
 }
 
 /* Decode a number */
-long
+static long
 decode(unsigned char **cpp)
 {
 	register int x;