Bronx-native, Greg Armstrong, 62, traces his Knicks fandom back to 1973, the same year the team last won a championship. Now living in Middletown, NY, he’s in his 34th year as a season ticket holder . He told The Post that his earliest memories go back to watching games on Channel 9 with his older brother, a Clyde Frazier fan, whose posters covered their bedroom walls. That lifelong obsession hasn’t been cheap. Armstrong said his full-season tickets started at about $2,000 years ago. The