MADISON, Wis. (AP) – Governor Scott Walker has submitted a revised budget for the University of Wisconsin System that officially calls for freezing tuition over the next two years and additional spending cuts in light of news the university has a $650 million surplus.        The change in Walker’s budget proposal was outlined Wednesday in a letter from the governor’s Department of Administration to the Legislature’s Joint Finance Committee.   The letter says the net effect of the changes Walker is proposing will lower the university’s reserve fund by $136 million.  Walker had originally given UW System a $181 million funding increase over the next two years. But Wednesday’s letter indicates that increase will be cut to about $87 million.