x86: Let x2APIC support depend on interrupt remapping or guest support

We are able to use x2APIC mode in the absence of interrupt remapping on
certain hypervisors. So it is fine to disable IRQ_REMAP without having
to give up x2APIC support.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Link: http://lkml.kernel.org/r/55479709.4030901@siemens.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/Kconfig

@@ -340,7 +340,7 @@ config X86_FEATURE_NAMES
 
 config X86_X2APIC
 	bool "Support x2apic"
-	depends on X86_LOCAL_APIC && X86_64 && IRQ_REMAP
+	depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
 	---help---
 	  This enables x2apic support on CPUs that have this feature.