The Church of Jesus Christ of Latter-days Saints has no position on Muhammad. It is not a topic that saves souls and such the Church has no interest in it.  
 
What we do preach though is that Jesus Christ the firstborn in Spirit and Only Begotten in the Flesh of Heavenly Father did come to restore his Church to the Earth after it's loss due to the apostasy of Israel. He also came again in 1820 to visit the boy Prophet Joseph Smith to prepare him to restore the same Church lost again to apostasy. So while we have no stance on if Muhammad was or was not a prophet of God, we do reject the claim that he was the Last of the prophets. We strongly believe that God would never cease sending his prophets to the Earth when man is prepared for them.