isisd: update struct isis_sr_psid_info with algorithm id

isisd: update struct isis_sr_psid_info with algorithm id

The information in prefix-sid has a new property
called algorithm id.  This is used to identify
the algorithm that separates it in the same IGP
network. This is used in Flex-Algo.In all other
cases, the algorithm id is basically 0.

Signed-off-by: Hiroki Shirokura <hiroki.shirokura@linecorp.com>
Signed-off-by: Eric Kinzie <ekinzie@labn.net>
Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>