During the recent discussion of taking 'volatile' off of the spinlock, I
noticed that while most arches #define cpu_relax() such that it implies
barrier(), some arches define cpu_relax() to be empty.

This patch changes the definition of cpu_relax() for frv, h8300, m68knommu,
sh, sh64, v850 and xtensa from an empty while(0) to the compiler barrier().
Signed-off-by: NChase Venters <chase.venters@clientec.com>
Acked-by: NArjan van de Ven <arjan@Linux.intel.com>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>