fbmon: remove unnecessary local variable

This fixes a sparse warning about symbol 'i' shadowing an earlier one.

Signed-off-by: Andre Haupt <andre@bitwigglers.org>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>