IB: Change CQE "csum_ok" field to a bit flag

Use a bit in wc_flags rather then a whole integer to hold the
"checksum OK" flag.  By itself, this change doesn't reduce the size of
struct ib_wc on 64bit machines -- it stays on 56 bytes because of
padding.  However, it will allow to add more fields in the future
without enlarging the struct.  Also, it will let us have a unified
approach with future libibverbs checksum offload reporting, because a
bit flag doesn't break the library ABI.

This patch was suggested during conversation with Liran Liss
<liranl@mellanox.com>.

Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Reviewed-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

include/rdma/ib_verbs.h

diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index ff22a73..c3cca5a 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -518,6 +518,7 @@
 	IB_WC_GRH		= 1,
 	IB_WC_WITH_IMM		= (1<<1),
 	IB_WC_WITH_INVALIDATE	= (1<<2),
+	IB_WC_IP_CSUM_OK	= (1<<3),
 };
 
 struct ib_wc {
@@ -538,7 +539,6 @@
 	u8			sl;
 	u8			dlid_path_bits;
 	u8			port_num;	/* valid only for DR SMPs on switches */
-	int			csum_ok;
 };
 
 enum ib_cq_notify_flags {