Satan now realizes that the only way he can earn God's forgiveness is to admit he was wrong. This means that he would have to ask for repentance and not simply be pardoned by God. He would have to surrender himself to God's rules which is what he could not do before. Also, Satan's pride forbids him to do this, because it would make him a coward in the eyes of the other angels he led. The phrase "None for pardon left" is Satan wondering if God could just forget the whole thing ever happened. 

Submission- to place under the authority of another; surrender.