mlxsw: Convert resources into array

Since the number of resources is going to get much bigger, ease up the
addition by simly defining IDs. Convert the existing structure members
to a set array, one for validity, one for values. Introduce a set of
getters and setters for easy access.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>