IB/rdmavt: Annotate rvt_reset_qp()

This patch avoids that sparse reports the following warning:

rdmavt/qp.c:507:17: warning: context imbalance in 'rvt_reset_qp' - unexpected unlock

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Mike Marciniszyn <mike.marciniszyn@intel.com>
Cc: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>