x86/init: Add intr_mode_init to x86_init_ops

X86 and XEN initialize interrupt delivery mode in different way.

To avoid conditionals, add a new x86_init_ops function which defaults to
the standard function and can be overridden by the early XEN platform code.

[ tglx: Folded the XEN part which was a separate patch to preserve
  	bisectability ]

Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: yinghai@kernel.org
Cc: bhe@redhat.com
Link: https://lkml.kernel.org/r/1505293975-26005-10-git-send-email-douly.fnst@cn.fujitsu.com

diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 69b9def..73f809a 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1230,6 +1230,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
 	x86_platform.get_nmi_reason = xen_get_nmi_reason;
 
 	x86_init.resources.memory_setup = xen_memory_setup;
+	x86_init.irqs.intr_mode_init	= x86_init_noop;
 	x86_init.oem.arch_setup = xen_arch_setup;
 	x86_init.oem.banner = xen_banner;