GPIO and MPUIO wake updates:

 - Hook MPUIOs into the irq wakeup framework too.  This uses a platform
   device to update irq enables during system sleep states, instead of
   a sys_device, since the latter is no longer needed for such things.

 - Also forward enable/disable irq wake requests to the relevant GPIO
   controller, so the top level IRQ dispatcher can (eventually) handle
   these wakeup events automatically if more than one GPIO pin needs to
   be a wakeup event source.

 - Minor tweak to the 24xx non-wakeup gpio stuff: no need to check such
   read-only data under the spinlock.

This assumes (maybe wrongly?) that only 16xx can do GPIO wakeup; without
a 15xx I can't test such stuff.

Also this expects the top level IRQ dispatcher to properly handle requests
to enable/disable irq wake, which is currently known to be wrong:  omap1
saves the flags but ignores them, omap2 doesn't even save it.  (Wakeup
events are, wrongly, hardwired in the relevant mach-omapX/pm.c file ...)
So MPUIO irqs won't yet trigger system wakeup.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Tony Lindgren <tony@atomide.com>