ia32: Do not add two keep edges in x87_kill_deads().
ia32: Do not add two keep edges in x87_kill_deads().

x87_create_fpop() already keeps the added fstp.

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