RDMA/IWPM: refactor the IWPM message attribute names

In order to add new IWPM_NL attributes, the enums for the IWPM commands
attributes are refactored such that a new attribute can be added without
breaking ABI version 3. Instead of sharing nl attribute enums for both
request and response messages, we create separate enums for each IWPM
message request and reply.  This allows us to extend any given IWPM
message by adding new attributes for just that message.  These new enums
are created, though, in a way to avoid breaking ABI version 3.

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Reviewed-by: Tatyana Nikolova <Tatyana.E.Nikolova@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>