x86/x2apic: remove usage of ACPI_FADT_APIC_CLUSTER

The ACPI FADT APIC_CLUSTER flag mandates that when the interrupt delivery is
Logical mode APIC must be configured for Cluster destination model.  However in
apic_x2apic_probe() such flag is incorrectly used to gate whether Physical mode
can be used.

Since Xen when in x2APIC mode only uses Logical mode together with Cluster
model completely remove checking for ACPI_FADT_APIC_CLUSTER, as Xen always
fulfills the requirement signaled by the flag.

Fixes: eb40ae41b6 ('x86/Kconfig: add option for default x2APIC destination mode')
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/genapic/x2apic.c

@@ -231,8 +231,7 @@ const struct genapic *__init apic_x2apic_probe(void)
          */
         x2apic_phys = iommu_intremap != iommu_intremap_full ||
                       (acpi_gbl_FADT.flags & ACPI_FADT_APIC_PHYSICAL) ||
-                      (IS_ENABLED(CONFIG_X2APIC_PHYSICAL) &&
-                       !(acpi_gbl_FADT.flags & ACPI_FADT_APIC_CLUSTER));
+                      IS_ENABLED(CONFIG_X2APIC_PHYSICAL);
     }
     else if ( !x2apic_phys )
         switch ( iommu_intremap )