RDMA/counter: Allow manual mode configuration support

In manual mode a QP is bound to a counter manually. If counter is not
specified then a new one will be allocated.

Manual mode is enabled when user binds a QP, and disabled when the last
manually bound QP is unbound.

When auto-mode is turned off and there are counters left, manual mode is
enabled so that the user is able to access these counters.

Signed-off-by: Mark Zhang <markz@mellanox.com>
Reviewed-by: Majd Dibbiny <majd@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>