From: Martin Schwidefsky <schwidefsky@de.ibm.com>

s390 inline assembly bug-fixes:

- Add memory barriers to spinlocks, atomic variable functions and to
  test_and_{set,clear,change}_bit.

- Add "=m" and "m" contraints to tell gcc that the content of a variable
  is in fact used.

- Replace "+m" constraints by "=m" on the output and "m" on the input list.

- Use c-implemtation for ffz and __ffs.

- Use generic c-implemtation for ffs and fls.