x86: Move UCLASS_IRQ into a separate file

Update this uclass to support the needs of the Apollo Lake ITSS. It
supports four operations.

Move the uclass into a separate directory so that sandbox can use it too.
Add a new Kconfig to control it and enable this on x86.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/cpu/irq.c

@@ -370,8 +370,3 @@ U_BOOT_DRIVER(irq_router_drv) = {
 	.probe		= irq_router_probe,
 	.priv_auto_alloc_size = sizeof(struct irq_router),
 };
-
-UCLASS_DRIVER(irq) = {
-	.id		= UCLASS_IRQ,
-	.name		= "irq",
-};