tipc: make msg_set_redundant_link() consistent with other set ops

All the other boolean like msg_set_X(m) operations don't
export both a msg_set_X(a) and a msg_clear_X(m), but instead
just have the single msg_set_X(m, val) variant.

Make the redundant_link one consistent by having the set take
a value, and delete the msg_clear_redundant_link() anomoly.
This is a cosmetic change and should not change behaviour.

Signed-off-by: Allan Stephens <Allan.Stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>