devlink: Add param set command

Add param set command to set value for a parameter.
Value can be set to any of the supported configuration modes.

Signed-off-by: Moshe Shemesh <moshe@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>