RDMA/cma: Make the locking for automatic state transition more clear

Re-organize things so the state variable is not read unlocked. The first
attempt to go directly from ADDR_BOUND immediately tells us if the ID is
already bound, if we can't do that then the attempt inside
rdma_bind_addr() to go from IDLE to ADDR_BOUND confirms the ID needs
binding.

Link: https://lore.kernel.org/r/20200902081122.745412-3-leon@kernel.org


Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>