By Frank Pingue (Reuters) – The PGA Tour has suspended all current and future players who have decided to join the Saudi-backed LIV Golf Invitational Series that began on Thursday. PGA Tour Commissioner Jay Monahan sent a letter to members that said those who join the lucrative breakaway series will not be permitted to play on the U.S.-based circuit as a non-member via a sponsor exemption or any other eligibility category. Among the players who have already joined LIV Golf are Phil Mickelson, who counts six major championships among his 45 PGA Tour wins, and former world number one Dustin John…