[LINUX] Fix interaction between idle loop and RCU subsystem.
There is a problem with the current implementation of stop_hz_timer in
arch/i386/kernel/time-xen.c where the hz timer can be stopped on a CPU
which has RCU callbacks pending.
This patch backports a new RCU API created to fix this problem for the
s390 implementation of stop_hz_timer and also updates the time-xen.c
implementation of stop_hz_timer to call the new API.
Signed-off-by: Harry Butterworth <butterwo@uk.ibm.com>