MIPS: Loongson: Remove unused macro LOONGSON_PERFCNT_IRQ

LOONGSON2_PERFCNT_IRQ is used for the irq number of the performance
overflow interrupts; LOONGSON_PERFCNT_IRQ is unused so remove it.
Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1494/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/loongson/lemote-2f/irq.c

@@ -19,7 +19,6 @@
 #include <machine.h>
 
 #define LOONGSON_TIMER_IRQ	(MIPS_CPU_IRQ_BASE + 7)	/* cpu timer */
-#define LOONGSON_PERFCNT_IRQ	(MIPS_CPU_IRQ_BASE + 6)	/* cpu perf counter */
 #define LOONGSON_NORTH_BRIDGE_IRQ	(MIPS_CPU_IRQ_BASE + 6)	/* bonito */
 #define LOONGSON_UART_IRQ	(MIPS_CPU_IRQ_BASE + 3)	/* cpu serial port */
 #define LOONGSON_SOUTH_BRIDGE_IRQ	(MIPS_CPU_IRQ_BASE + 2)	/* i8259 */