IB/ipath: Fix potentially wrong RNR retry counter returned in ipath_query_qp()

There can be a case where the requester's rnr retry counter
(s_rnr_retry) is less than the number of rnr retries allowed per QP
(s_rnr_retry_cnt).  This can happen if the s_rnr_retry counter is being
decremented and an ipath_query_qp call is issued during that time frame.
The fix is to always return the number of rnr retries allowed per QP
instead of the requester's rnr counter.

Found by code review.

Signed-off-by: Patrick Marchand Latifi <patrick.latifi@qlogic.com>
Acked-by: Ralph Campbell <ralph.campbell@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>