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 IA-64-specific values

 CT_DoArchTupleValues() {

     # The architecture part of the tuple:

     CT_TARGET_ARCH="${CT_ARCH}"

 }