igb: Replace LRO with GRO

This patch makes igb invoke the GRO hooks instead of LRO.  As
GRO has a compatible external interface to LRO this is a very
straightforward replacement.

Three things of note:

1) I've kept the LRO Kconfig option until we decide to enable
GRO across the board at which point it can also be killed.

2) The poll_controller stuff is broken in igb as it tries to do
the same work as the normal poll routine.  Since poll_controller
can be called in the middle of a poll, this can't be good.

I noticed this because poll_controller can invoke the GRO hooks
without flushing held GRO packets.

However, this should be harmless (assuming the poll_controller
bug above doesn't kill you first :) since the next ->poll will
clear the backlog.  The only time when we'll have a problem is
if we're already executing the GRO code on the same ring, but
that's no worse than what happens now.

3) I kept the ip_summed check before calling GRO so that we're
on par with previous behaviour.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/igb/igb.h

@@ -36,12 +36,6 @@
 
 struct igb_adapter;
 
-#ifdef CONFIG_IGB_LRO
-#include <linux/inet_lro.h>
-#define MAX_LRO_AGGR                      32
-#define MAX_LRO_DESCRIPTORS                8
-#endif
-
 /* Interrupt defines */
 #define IGB_MIN_DYN_ITR 3000
 #define IGB_MAX_DYN_ITR 96000
@@ -176,10 +170,6 @@ struct igb_ring {
 			struct napi_struct napi;
 			int set_itr;
 			struct igb_ring *buddy;
-#ifdef CONFIG_IGB_LRO
-			struct net_lro_mgr lro_mgr;
-			bool lro_used;
-#endif
 		};
 	};
 
@@ -288,12 +278,6 @@ struct igb_adapter {
 	int need_ioport;
 
 	struct igb_ring *multi_tx_table[IGB_MAX_TX_QUEUES];
-#ifdef CONFIG_IGB_LRO
-	unsigned int lro_max_aggr;
-	unsigned int lro_aggregated;
-	unsigned int lro_flushed;
-	unsigned int lro_no_desc;
-#endif
 	unsigned int tx_ring_count;
 	unsigned int rx_ring_count;
 };