[S390] s390: rename CPU_IDLE to S390_CPU_IDLE

sched-cfs-v2.6.22-git-v18.patch introduces CPU_IDLE in sched.h.
This conflict with the already existing define in
include/asm-s390/processor.h
Just rename the s390 defines, since they will go away as soon as
we support CONFIG_NO_HZ instead of our own CONFIG_NO_IDLE_HZ.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>