arch/s390: cleanups

Don't select unneeded config knobs. Don't select non-existing config knobs.
Use the "no patch" config knob, instead of pointing to an non-exiting local
patch dir. Simplify the tuple-related scripts. Update the samples.

 # Compute s390-specific values

 CT_DoArchTupleValues() {

     # Defaults are all OK for s390

     :

 }