net/tipc: remove redundant variables 'tn' and 'oport'

Variables 'tn' and 'oport'  are being assigned but are never used hence
they are redundant and can be removed.

Cleans up clang warnings:
warning: variable 'oport' set but not used [-Wunused-but-set-variable]
warning: variable 'tn' set but not used [-Wunused-but-set-variable]

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>