RDMA/iwcm: Release resources if iw_cm module initialization fails

RDMA/iwcm: Release resources if iw_cm module initialization fails

[ Upstream commit e677b72a0647249370f2635862bf0241c86f66ad ]

The failure during iw_cm module initialization partially left the system
with unreleased memory and other resources. Rewrite the module init/exit
routines in such way that netlink commands will be opened only after
successful initialization.

Fixes: 5c0f00dad781 ("iwcm: common code for port mapper")
Link: https://lore.kernel.org/r/b01239f99cb1a3e6d2b0694c242d89e6410bcd93.1627048781.git.leonro@nvidia.com
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>