IB/core: type promotion bug in rdma_rw_init_one_mr()

IB/core: type promotion bug in rdma_rw_init_one_mr()

[ Upstream commit c2d7c8ff89b22ddefb1ac2986c0d48444a667689 ]

"nents" is an unsigned int, so if ib_map_mr_sg() returns a negative
error code then it's type promoted to a high unsigned int which is
treated as success.

Fixes: a060b5629ab0 ("IB/core: generic RDMA READ/WRITE API")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>