ACPI: Enhance /sys/firmware/interrupts to allow enable/disable/clear from user-space

Allow users to enable/disable/clear a specific & valid GPE/Fixed Event
in user space.

This is useful for debugging, especially for some
interrupt storm issues.

All wakeup GPEs are disabled and they can not be enabled at runtime,
and we mark them as invalid.

All GPEs that don't have a _Lxx/_Exx method are marked as invalid.

All Fixed Events that don't have an event handler are marked as invalid
and they can't be enabled until an event handler is registered.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Ling Ming <ming.m.lin@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>