twl4030 power button irq

Disable the TWL4030_PWRIRQ_PWRBTN symbol from the system headers;
initialization of the power button handler still needs work, so
an equivalent symbol is defined in its driver.

Power IRQs now properly handle trigger specs from request_irq();
stop goofing with registers reserved to the IRQ infrastructure.

Minor cleanup:  switch several messages to pr_debug().

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