MIPS: ath79: Remove useless #ifdef CONFIG_IRQCHIP

MIPS: ath79: Remove useless #ifdef CONFIG_IRQCHIP

IRQCHIP is always enabled, so the #ifdef can just be removed.

Signed-off-by: Alban Bedel <albeu@free.fr>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Alexander Couzens <lynxis@fe80.eu>
Cc: Joel Porquet <joel@porquet.org>
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/11504/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>