x86/apic: Only disable CPU x2apic mode when necessary

x86/apic: Only disable CPU x2apic mode when necessary

When interrupt remapping hardware is not in X2APIC, CPU X2APIC mode
will be disabled if:
1) Maximum CPU APIC ID is bigger than 255
2) hypervisior doesn't support x2apic mode.

But we should only check whether hypervisor supports X2APIC mode when
hypervisor(CONFIG_HYPERVISOR_GUEST) is enabled, otherwise X2APIC will
always be disabled when CONFIG_HYPERVISOR_GUEST is disabled and IR
doesn't work in X2APIC mode.

Signed-off-by: Jiang Liu <[email protected]>
Tested-by: Joerg Roedel <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: [email protected]
Cc: H. Peter Anvin <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Yinghai Lu <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: HATAYAMA Daisuke <[email protected]>
Cc: Jan Beulich <[email protected]>
Cc: Richard Weinberger <[email protected]>
Cc: Oren Twaig <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>