drivers/net/tokenring: fix sparse warning: symbol shadows an earlier one

Impact: Remove redundant variables.

Fix this sparse warnings:
  drivers/net/tokenring/lanstreamer.c:619:21: warning: symbol 'i' shadows an earlier one
  drivers/net/tokenring/lanstreamer.c:589:13: originally declared here
  drivers/net/tokenring/madgemc.c:695:34: warning: symbol 'tp' shadows an earlier one
  drivers/net/tokenring/madgemc.c:689:26: originally declared here
  drivers/net/tokenring/olympic.c:702:21: warning: symbol 'i' shadows an earlier one
  drivers/net/tokenring/olympic.c:440:13: originally declared here

Signed-off-by: Hannes Eder <hannes@hanneseder.net>
Signed-off-by: David S. Miller <davem@davemloft.net>