net: Convert LIMIT_NETDEBUG to net_dbg_ratelimited

Use the more common dynamic_debug capable net_dbg_ratelimited
and remove the LIMIT_NETDEBUG macro.

All messages are still ratelimited.

Some KERN_<LEVEL> uses are changed to KERN_DEBUG.

This may have some negative impact on messages that were
emitted at KERN_INFO that are not not enabled at all unless
DEBUG is defined or dynamic_debug is enabled.  Even so,
these messages are now _not_ emitted by default.

This also eliminates the use of the net_msg_warn sysctl
"/proc/sys/net/core/warnings".  For backward compatibility,
the sysctl is not removed, but it has no function.  The extern
declaration of net_msg_warn is removed from sock.h and made
static in net/core/sysctl_net_core.c

Miscellanea:

o Update the sysctl documentation
o Remove the embedded uses of pr_fmt
o Coalesce format fragments
o Realign arguments

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
index d21d7b2..d2c2d74 100644
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -286,8 +286,8 @@
 	err = -EINVAL;
 	padlen = nexthdr[0];
 	if (padlen + 2 + alen >= elen) {
-		LIMIT_NETDEBUG(KERN_WARNING "ipsec esp packet is garbage "
-			       "padlen=%d, elen=%d\n", padlen + 2, elen - alen);
+		net_dbg_ratelimited("ipsec esp packet is garbage padlen=%d, elen=%d\n",
+				    padlen + 2, elen - alen);
 		goto out;
 	}