tools/times.sh: adapt comment to the actual loops

left over from #ea9f0718

Signed-off-by: Toralf Förster <toralf.foerster@gmx.de>
tools/times.sh: prefer a loop over repeating the same command

Signed-off-by: Toralf Förster <toralf.foerster@gmx.de>
tools/times.sh: use always long-opts

Signed-off-by: Toralf Förster <toralf.foerster@gmx.de>
tools/times.sh: exit if prereq were not met

Signed-off-by: Toralf Förster <toralf.foerster@gmx.de>
Merge pull request #347 from toralf/timer

Timer