mlxsw: pci: Add support for getting resource through devlink

Up until now the KVD partition was static. This patch introduces the
ability to get the resource sizes via devlink. In case the resource is not
available the default configuration is used.

Signed-off-by: Arkadi Sharshevsky <arkadis@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>