This adjusts i386's cmpxchg patterns so that

- for word and long cmpxchg-es the compiler can utilize all possible
  registers

- cmpxchg8b gets disabled when the minimum specified hardware architectur
  doesn't support it (like was already happening for the byte, word, and
  long ones).
Signed-off-by: NJan Beulich <jbeulich@novell.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>