Remove redundant operations from set_phi_arguments(): phi is always a Phi.
Remove redundant operations from set_phi_arguments(): phi is always a Phi.

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