execfreq: Remove unnecessary fabs().
execfreq: Remove unnecessary fabs().

The result of gs_matrix_gauss_seidel() never is negative.

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