dm: x86: Add a common PIRQ init function

Most x86 interrupt drivers will want to use the standard PIRQ routing and
table setup. Put this code in a common function so it can be used by those
drivers that want it.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/cpu/irq.c b/arch/x86/cpu/irq.c
index 8f59b23..e2feba7 100644
--- a/arch/x86/cpu/irq.c
+++ b/arch/x86/cpu/irq.c
@@ -231,7 +231,7 @@
 	return 0;
 }
 
-int irq_router_probe(struct udevice *dev)
+int irq_router_common_init(struct udevice *dev)
 {
 	int ret;
 
@@ -249,6 +249,11 @@
 	return 0;
 }
 
+int irq_router_probe(struct udevice *dev)
+{
+	return irq_router_common_init(dev);
+}
+
 u32 write_pirq_routing_table(u32 addr)
 {
 	if (!pirq_routing_table)