Review of qib_ruc_check_hdr() shows that the s_lock is not required in
the normal case.  The r_lock is held in all cases, and protects the qp
fields that are read.

The s_lock will be needed to around the call to qib_migrate_qp() to
insure that the send engine sees a consistent set of fields.
Signed-off-by: NMike Marciniszyn <mike.marciniszyn@qlogic.com>
Signed-off-by: NRoland Dreier <roland@purestorage.com>