devlink: Refactor validation of finding required arguments

devlink: Refactor validation of finding required arguments

Introducing argument's metadata structure matching a bitmap flag per
required argument and an error message if missing. Using this static
array to refactor validation of finding required arguments in devlink
command line and to ease further maintenance.

Signed-off-by: Aya Levin <ayal@mellanox.com>
Reviewed-by: Moshe Shemesh <moshe@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David Ahern <dsahern@gmail.com>