Fix incorrect comment

Fix incorrect comment

target_start_algorithm does not download the algorithm. It only starts
it. It expects someone else to have already written the algorithm code
into the proper location before calling it.

Change-Id: I5e04406eed0ebb1c23e550dbf8d9f1204c432603
Signed-off-by: Christopher Head <chead@zaber.com>
Reviewed-on: http://openocd.zylin.com/4435
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>