router: remove some log spam in send_router_advert()

router: remove some log spam in send_router_advert()

Both these messages would otherwise be printed on each RA.

Especially the second one merely means that we're follwing the cfg
explicitly set by the user, so they're not very likely to be interested
to know that we're doing what we've been told to do.

Signed-off-by: David Härdeman <[email protected]>
Link: https://github.com/openwrt/odhcpd/pull/358
Signed-off-by: Álvaro Fernández Rojas <[email protected]>