MIPS: ath79: irq: IRQCHIP_DECLARE moved to linux/irqchip.h

Remove the ugly cross tree include now that IRQCHIP_DECLARE moved to
linux/irqchip.h.

Signed-off-by: Alban Bedel <albeu@free.fr>
Cc: linux-mips@linux-mips.org
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: Qais Yousef <qais.yousef@imgtec.com>
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/10633/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>