IB/core: Introduce delay drop for a WQ

Work queue which is created with IB_WQ_FLAGS_DELAY_DROP won't
cause packet drops when there aren't receive WQEs, but will wait until
posting of receive WQEs or for some period of time that the device
was configured with.

It includes:
 * Add a new creation flag to enable delay drop functionality in a WQ.
 * A new capability was introduced - IB_RAW_PACKET_CAP_DELAY_DROP, which
   is the device's ability to delay packet drops when there aren't receive
   WQEs.
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Reviewed-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>

include/rdma/ib_verbs.h

@@ -1546,6 +1546,10 @@ enum ib_raw_packet_caps {
 	IB_RAW_PACKET_CAP_SCATTER_FCS		= (1 << 1),
 	/* Checksum offloads are supported (for both send and receive). */
 	IB_RAW_PACKET_CAP_IP_CSUM		= (1 << 2),
+	/* When a packet is received for an RQ with no receive WQEs, the
+	 * packet processing is delayed.
+	 */
+	IB_RAW_PACKET_CAP_DELAY_DROP		= (1 << 3),
 };
 
 enum ib_wq_type {
@@ -1574,6 +1578,7 @@ struct ib_wq {
 enum ib_wq_flags {
 	IB_WQ_FLAGS_CVLAN_STRIPPING	= 1 << 0,
 	IB_WQ_FLAGS_SCATTER_FCS		= 1 << 1,
+	IB_WQ_FLAGS_DELAY_DROP		= 1 << 2,
 };
 
 struct ib_wq_init_attr {