bridge: mdb: add support for extended router port information

bridge: mdb: add support for extended router port information

Recently a new temp router port mode was added and with it the dumped
information was extended similar to how mdb entries were done. This
patch adds support to dump the new information by using the "-s" switch.
Example:
$ bridge -d -s mdb show
dev br0 port eth1 grp ff02::1:ffbf:5716 temp 234.39
dev br0 port eth1 grp 239.0.0.2 temp  97.17
dev br0 port eth1 grp 239.0.0.3 temp 105.36
router ports on br0: eth1    0.00 permanent
router ports on br0: eth2  254.87 temp

It also updates the bridge man page.

Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>