resource: Add irqresource_disabled()

Add a common function to set the fields for a irq resource to disabled,
which mimics what is done in acpi_dev_irqresource_disabled(), with a view
to replace that function.
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/1606905417-183214-3-git-send-email-john.garry@huawei.com

include/linux/ioport.h

@@ -307,6 +307,13 @@ struct resource *devm_request_free_mem_region(struct device *dev,
 struct resource *request_free_mem_region(struct resource *base,
 		unsigned long size, const char *name);
 
+static inline void irqresource_disabled(struct resource *res, u32 irq)
+{
+	res->start = irq;
+	res->end = irq;
+	res->flags = IORESOURCE_IRQ | IORESOURCE_DISABLED | IORESOURCE_UNSET;
+}
+
 #ifdef CONFIG_IO_STRICT_DEVMEM
 void revoke_devmem(struct resource *res);
 #else