iropt: fix direct calls to compute_cmp
iropt: fix direct calls to compute_cmp

- The direct call did not respect the get_opt_constant_folding() flag

killbug2004/libfirm,libfirm/libfirm,davidgiven/libfirm,MatzeB/libfirm,davidgiven/libfirm,davidgiven/libfirm,libfirm/libfirm,8l/libfirm,jonashaag/libfirm,MatzeB/libfirm,killbug2004/libfirm,jonashaag/libfirm,jonashaag/libfirm,8l/libfirm,8l/libfirm,8l/libfirm,8l/libfirm,libfirm/libfirm,davidgiven/libfirm,killbug2004/libfirm,davidgiven/libfirm,libfirm/libfirm,killbug2004/libfirm,MatzeB/libfirm,killbug2004/libfirm,MatzeB/libfirm,8l/libfirm,jonashaag/libfirm,libfirm/libfirm,jonashaag/libfirm,davidgiven/libfirm,8l/libfirm,MatzeB/libfirm,MatzeB/libfirm,jonashaag/libfirm,killbug2004/libfirm,MatzeB/libfirm,killbug2004/libfirm,davidgiven/libfirm,jonashaag/libfirm