ripd: use only one constant for derivation

RIP_MAX_RTE is defined in ripd.h as 25 but is in fact the
result of a formula. More over it is not used in the code:
the code itself includes the fomula. This makes it un-clear
for maintenance.

Signed-off-by: Feng Lu <lu.feng@6wind.com>
Reviewed-by: Alain Ritoux <alain.ritoux@6wind.com>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
2 files changed