lib/kstrtox.c: remove redundant cleanup

We can't reach the cleanup code unless the flag KSTRTOX_OVERFLOW is not
set, so there's not no point in clearing a bit that we know is not set.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Acked-by: Levente Kurusa <levex@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>