IB/hfi1: Compute BTH only for RDMA_WRITE_LAST/SEND_LAST packet

In hfi1_rc_rcv(), BTH is computed for all packets received.
However, it's only used for packets received with opcodes
RDMA_WRITE_LAST and SEND_LAST, and it is a costly operation.

Compute BTH only in the RDMA_WRITE_LAST/SEND_LAST code path
and let the compiler handle endianness conversion for bitwise
operations.

Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Sebastian Sanchez <sebastian.sanchez@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/qib/qib_ud.c

@@ -581,8 +581,7 @@ void qib_ud_rcv(struct qib_ibport *ibp, struct ib_header *hdr,
 	wc.port_num = qp->port_num;
 	/* Signal completion event if the solicited bit is set. */
 	rvt_cq_enter(ibcq_to_rvtcq(qp->ibqp.recv_cq), &wc,
-		     (ohdr->bth[0] &
-			cpu_to_be32(IB_BTH_SOLICITED)) != 0);
+		     ib_bth_is_solicited(ohdr));
 	return;
 
 drop: