[TIPC]: Fix two minor sparse warnings.

fix two warnings generated by sparse:

link.c:2386 symbol 'msgcount' shadows an earlier one
node.c:244 symbol 'addr_string' shadows an earlier one

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>