irqdomain: Kill CONFIG_IRQ_DOMAIN_DEBUG

CONFIG_IRQ_DOMAIN_DEBUG is similar to CONFIG_GENERIC_IRQ_DEBUGFS,
just with less information.

Spring cleanup time.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Yang Shunyong <shunyong.yang@hxt-semitech.com>
Link: https://lkml.kernel.org/r/20180117142647.23622-1-marc.zyngier@arm.com