[NET]: Add NETIF_F_GEN_CSUM and NETIF_F_ALL_CSUM

The current stack treats NETIF_F_HW_CSUM and NETIF_F_NO_CSUM
identically so we test for them in quite a few places.  For the sake
of brevity, I'm adding the macro NETIF_F_GEN_CSUM for these two.  We
also test the disjunct of NETIF_F_IP_CSUM and the other two in various
places, for that purpose I've added NETIF_F_ALL_CSUM.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index d4bb3fa..8538aac 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -840,7 +840,7 @@
 	 */
 	if (transhdrlen &&
 	    length + fragheaderlen <= mtu &&
-	    rt->u.dst.dev->features&(NETIF_F_IP_CSUM|NETIF_F_NO_CSUM|NETIF_F_HW_CSUM) &&
+	    rt->u.dst.dev->features & NETIF_F_ALL_CSUM &&
 	    !exthdrlen)
 		csummode = CHECKSUM_HW;