x86, intel-iommu: fix X2APIC && !ACPI build failure

This build failure:

| drivers/pci/dmar.c:47: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘dmar_tbl_size’
| drivers/pci/dmar.c:62: warning: ‘struct acpi_dmar_device_scope’ declared inside parameter list
| drivers/pci/dmar.c:62: warning: its scope is only this definition or declaration, which is probably not what you want

Triggers due to this commit:

  d0b03bd: x2apic/intr-remap: decouple interrupt remapping from x2apic

Which exposed a pre-existing but dormant fragility of the 'select X86_X2APIC'
it moved around and turned that fragility into a build failure.

Replace it with a proper 'depends on' construct.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
LKML-Reference: <1239084280.22733.404.camel@macbook.infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/Kconfig

@@ -252,17 +252,13 @@ config SMP
 
 config X86_X2APIC
 	bool "Support x2apic"
-	depends on X86_LOCAL_APIC && X86_64
-	select INTR_REMAP
+	depends on X86_LOCAL_APIC && X86_64 && INTR_REMAP
 	---help---
 	  This enables x2apic support on CPUs that have this feature.
 
 	  This allows 32-bit apic IDs (so it can support very large systems),
 	  and accesses the local apic via MSRs not via mmio.
 
-	  ( On certain CPU models you may need to enable INTR_REMAP too,
-	    to get functional x2apic mode. )
-
 	  If you don't know what to do here, say N.
 
 config SPARSE_IRQ