tipc: fix incompatible mtu of transmission

In commit 682cd3cf
("tipc: confgiure and apply UDP bearer MTU on running links"), we
introduced a function to change UDP bearer MTU and applied this new value
across existing per-link. However, we did not apply this new MTU value at
node level. This lead to packet dropped at link level if its size is
greater than new MTU value.

To fix this issue, we also apply this new MTU value for node level.

Fixes: 682cd3cf ("tipc: confgiure and apply UDP bearer MTU on running links")
Acked-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: Hoang Le <hoang.h.le@dektech.com.au>
Link: https://lore.kernel.org/r/20201130025544.3602-1-hoang.h.le@dektech.com.au


Signed-off-by: Jakub Kicinski <kuba@kernel.org>