dt-bindings: interrupt-controller: Remove obsolete 'img,meta-intc'

The driver and metag arch were removed in 2018.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200826184851.3431531-3-robh@kernel.org


Signed-off-by: Rob Herring <robh@kernel.org>