drivers/irqchip: Remove EZChip NPS interrupt controller

NPS platform has been removed from ARC port and there are no in-tree
users of it now. So RIP !

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <maz@kernel.org>
Cc: linux-kernel@vger.kernel.org
Link: https://lore.kernel.org/r/20201105212210.1891598-3-vgupta@synopsys.com