minor irq-related cleanups

Minor IRQ-related cleanups:  comment out the no-longer-used
GPIO irq symbol (more to come, eventually); create RTC IRQ
resource; and use that RTC IRQ resource.

And incidentally, make the RTC code free the correct IRQ;
it was pretty goofed up...

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Felipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>