[PATCH] ppc32: support hotplug cpu on powermacs

This allows cpus to be off-lined on 32-bit SMP powermacs.  When a cpu
is off-lined, it is put into sleep mode with interrupts disabled.  It
can be on-lined again by asserting its soft-reset pin, which is
connected to a GPIO pin.

With this I can off-line the second cpu in my dual G4 powermac, which
means that I can then suspend the machine (the suspend/resume code
refuses to suspend if more than one cpu is online, and making it cope
with multiple cpus is surprisingly messy).

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>