tipc: adjust tipc_nodeid2string() to return string length

tipc: adjust tipc_nodeid2string() to return string length

Since the value returned by 'tipc_nodeid2string()' is not used, the
function may be adjusted to return the length of the result, which
is helpful to drop a few calls to 'strlen()' in 'tipc_link_create()'
and 'tipc_link_bc_create()'. Compile tested only.

Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250926074113.914399-1-dmantipov@yandex.ru
Signed-off-by: Paolo Abeni <pabeni@redhat.com>