net: ethernet: sun: drop unused variable

Commit bfd428da

 ("net: ethernet: sun: initialize variables directly")
dropped the only loop that was using i but did not remove the actual
variable, therefore causing a warning when building. This patch drops
the now redundant line.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Emilio López <emilio@elopez.com.ar>
Signed-off-by: David S. Miller <davem@davemloft.net>