RDMA/counter: Add PID category support in auto mode

With the "PID" category QPs have same PID will be bound to same counter;
If this category is not set then QPs have different PIDs will be bound
to same counter.

This is implemented for 2 reasons:
1. The counter is a limited resource, while there may be dozens of
   applications, each of which creates several types of QPs, which means
   it may doesn't have enough counter.
2. The system administrator needs all QPs created by all applications
   with same type bound to one counter.

The counter name and PID is only make sense when "PID" category are
configured.

This category can also be used in combine with others, e.g. QP type.

Link: https://lore.kernel.org/r/20200702082933.424537-2-leon@kernel.org


Signed-off-by: Mark Zhang <markz@mellanox.com>
Reviewed-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>