sparc: Remove redundant panic.
sparc: Remove redundant panic.

The finish phase would panic already, when the matching constraint of cas is not fulfillable.

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