Handle activation of DASDs in linuxrc.s390 since loader no longer works
    
    Since we automatically load device drivers in linuxrc.s390 by means of
    udev, loader can no longer explicitly load the DASD device driver module
    and pass the module option DASD=... in order to activate DASDs
    based on the user specification in parm/conf file or interactively in
    linuxrc.s390.
    This patch does the necessary work in linuxrc.s390 including full
    support for usability features such as restarting configuration
    without reboot.
    In a next step we could remove the DASD module stuff from loader.
    
    It is recommended to use /dev/disk/by-* instead of /dev/dasdXY.