Besides, not every time one willingly acts in a way that brings about his own death, it is a suicide. A soldier in a war, for example, is not committing a suicide when bravery causes him his life.
The parallel here is not valid, annalex, because Christ could not die unless He willed Himself to die. But He did not commit the act of self-murder! And neither does your soldier. A soldier who dies in an act of heroism does not want to die even though he probably realizes he will.
Jesus' death, however, was necessary in order for it to be followed with a Resurrection, without which there would be no Chrisitanity. This is a tricky thing — for if we are to take it literally, people would be committing suicide all over the place! Christ died like any ordinary human being would die — from the wounds inflicted on Him, by His own permission.