RDMA/siw: Fix post_recv QP state locking

[ Upstream commit 0edefddbae396e50eb7887d279d0c4bb4d7a6384 ]

Do not release qp state lock if not previously acquired.

Fixes: cf049bb31f71 ("RDMA/siw: Fix SQ/RQ drain logic")
Link: https://lore.kernel.org/r/20191025142903.20625-1-bmt@zurich.ibm.com


Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Bernard Metzler <bmt@zurich.ibm.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>