[IPV4]: align inet_protos[] on SMP

As IPPROTO_TCP is 6, it makes sense to make sure inet_protos[] array
is properly cache line aligned to avoid false sharing on SMP.

c0680540 b peer_total
c0680544 b inet_peer_unused_head
c0680560 B inet_protos

On i386 this example, we can see that inet_protos[IPPROTO_TCP] shares
a potentially hot (and modified) cache line.
Signed-off-by: NEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/protocol.c

@@ -45,7 +45,7 @@
 #include <net/ipip.h>
 #include <linux/igmp.h>
 
-struct net_protocol *inet_protos[MAX_INET_PROTOS];
+struct net_protocol *inet_protos[MAX_INET_PROTOS] ____cacheline_aligned_in_smp;
 static DEFINE_SPINLOCK(inet_proto_lock);
 
 /*