RDS/IB: Remove dangling rcu_read_unlock() and other cleanups

RDS/IB: Remove dangling rcu_read_unlock() and other cleanups

Delete dangling rcu_read_unlock() which was left behind
when matching rcu_read_lock() and enclosed code was
removed in commit 538f5d0dfa704f4dcb4afa80a1d01b1317b9cd65

All compiler warnings are also fixed.

Orabug: 18995395

Signed-off-by: Mukesh Kacker <mukesh.kacker@oracle.com>
Reviewed-by: Rama Nichanamatlu <rama.nichanamatlu@oracle.com>
Signed-off-by: Guangyu Sun <guangyu.sun@oracle.com>
(cherry picked from commit ba3dcd2f88fbf554f77bb312727c88193decfb75)