[PATCH RFC v3] s390: convert to GENERIC_VDSO

[Sven Schnelle]

here's the third version of the generic vdso patchset for s390.

Changes in v3;
- update the architecture specific data patch to the correct one.

Changes in v2:
- added patch from Thomas that adds vdso_update_begin()/vdso_update_end()
- changed the s390 code to use the vdso update functions
- changed the name of the architecture specific data to 'arch_data'