MIPS: jz4740: Fix surviving instance of irq_to_gpio()

This is fallout from commit 832f5dacfa0b ("MIPS: Remove all the uses of
custom gpio.h").

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Suggested-by: Lars-Peter Clausen <lars@metafoo.de>

arch/mips/jz4740/gpio.c

@@ -270,7 +270,7 @@ uint32_t jz_gpio_port_get_value(int port, uint32_t mask)
 }
 EXPORT_SYMBOL(jz_gpio_port_get_value);
 
-#define IRQ_TO_BIT(irq) BIT(irq_to_gpio(irq) & 0x1f)
+#define IRQ_TO_BIT(irq) BIT((irq - JZ4740_IRQ_GPIO(0)) & 0x1f)
 
 static void jz_gpio_check_trigger_both(struct jz_gpio_chip *chip, unsigned int irq)
 {