x86/irq: Fix missing declaration of 'io_apic_irqs'

Fix this sparse warning:

  arch/x86/kernel/i8259.c:57:15: warning: symbol 'io_apic_irqs' was not declared. Should it be static?

Signed-off-by: Zhang Kunbo <zhangkunbo@huawei.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20241126020511.3464664-1-zhangkunbo@huawei.com

Author: Zhang Kunbo

arch/x86/kernel/i8259.c

@@ -23,6 +23,7 @@
 #include <asm/desc.h>
 #include <asm/apic.h>
 #include <asm/i8259.h>
+#include <asm/io_apic.h>
 
 /*
  * This is the 'legacy' 8259A Programmable Interrupt Controller,