- Hide cycle estimates behind a new flag, --verbose-cycle-estimate
- Update documentation to include the new flag
- Add notes highlighting that the estimates are only estimates and that
  for more accurate numbers the software model is suggested.

Change-Id: Id1342b71cca3ee11dead9a6fdf084fd2b5d030cb
Signed-off-by: Rickard Bolin <rickard.bolin@arm.com>