ia32: Remove unnecessary case distinction.
ia32: Remove unnecessary case distinction.

Simply always set the registers of all outputs of the new Add.

libfirm/libfirm,libfirm/libfirm,MatzeB/libfirm,jonashaag/libfirm,jonashaag/libfirm,MatzeB/libfirm,jonashaag/libfirm,libfirm/libfirm,MatzeB/libfirm,MatzeB/libfirm,MatzeB/libfirm,jonashaag/libfirm,MatzeB/libfirm,libfirm/libfirm,jonashaag/libfirm,jonashaag/libfirm,MatzeB/libfirm,jonashaag/libfirm,libfirm/libfirm