IB/hfi1: Don't zero out qp->s_ack_queue in rvt_reset_qp

Since rvt_reset_qp already zero's out qp->s_ack_queue head and tail
pointers, there is no need to zero out qp->s_ack_queue itself.

Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>