x86/apic: Correctly detect X2APIC status in function enable_IR()

X2APIC will be disabled if user specifies "nox2apic" on kernel command
line, even when x2apic_preenabled is true. So correctly detect X2APIC
status by using x2apic_enabled() instead of x2apic_preenabled.
Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: iommu@lists.linux-foundation.org
Cc: H. Peter Anvin <hpa@linux.intel.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: David Rientjes <rientjes@google.com>
Cc: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Cc: Jan Beulich <JBeulich@suse.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Oren Twaig <oren@scalemp.com>
Link: http://lkml.kernel.org/r/1420615903-28253-7-git-send-email-jiang.liu@linux.intel.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/apic/apic.c

@@ -1581,7 +1581,7 @@ int __init enable_IR(void)
 		return -1;
 	}
 
-	if (!x2apic_preenabled && skip_ioapic_setup) {
+	if (!x2apic_enabled() && skip_ioapic_setup) {
 		pr_info("Skipped enabling intr-remap because of skipping "
 			"io-apic setup\n");
 		return -1;