ppc: Remove orphan xilinx_irq.h file

This file is completely unused and it should be removed as the part of
ppc405/ppc440 xilinx platform removal.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/powerpc/include/asm/xilinx_irq.h

@@ -1,25 +0,0 @@
-/*
- * (C) Copyright 2008
- * Ricado Ribalda-Universidad Autonoma de Madrid-ricardo.ribalda@gmail.com
- * This work has been supported by: QTechnology  http://qtec.com/
- * Based on interrupts.c Wolfgang Denk-DENX Software Engineering-wd@denx.de
- * SPDX-License-Identifier:	GPL-2.0+
-*/
-#ifndef XILINX_IRQ_H
-#define XILINX_IRQ_H
-
-#define intc	XPAR_INTC_0_BASEADDR
-#define ISR	(intc + (0 * 4))	/* Interrupt Status Register */
-#define IPR	(intc + (1 * 4))	/* Interrupt Pending Register */
-#define IER	(intc + (2 * 4))	/* Interrupt Enable Register */
-#define IAR	(intc + (3 * 4))	/* Interrupt Acknowledge Register */
-#define SIE	(intc + (4 * 4))	/* Set Interrupt Enable bits */
-#define CIE	(intc + (5 * 4))	/* Clear Interrupt Enable bits */
-#define IVR	(intc + (6 * 4))	/* Interrupt Vector Register */
-#define MER	(intc + (7 * 4))	/* Master Enable Register */
-
-#define IRQ_MASK(irq)	(1 << (irq & 0x1f))
-
-#define IRQ_MAX		XPAR_INTC_MAX_NUM_INTR_INPUTS
-
-#endif