This does a bit of chainsawing of the idle loop code to get light sleep
working on SMP. Previously this was forcing secondary CPUs in to sleep
mode with them not coming back if they didn't have their own local
timers. Given that we use clockevents broadcasting by default, the CPU
managing the clockevents can't have IRQs disabled before entering its
sleep state.

This unfortunately leaves us with the age-old need_resched() race in
between local_irq_enable() and cpu_sleep(), but at present this is
unavoidable. After some more experimentation it may be possible to layer
on SR.BL bit manipulation over top of this scheme to inhibit the race
condition, but given the current potential for missing wakeups, this is
left as a future exercise.
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

Crib the x86 cpu_idle_wait() implementation and shove it in with the
idle code, subsequently enabling ARCH_HAS_CPU_IDLE_WAIT.
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

cpuidle wants ARCH_HAS_DEFAULT_IDLE defined in order to use the
default idle loop. So, make it accessible and enable it for all
sh machines.
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

Signed-off-by: NPaul Mundt <lethal@linux-sh.org>