x86, xen-swiotlb: Make Xen-SWIOTLB use IOMMU_INIT_* macros.

We utilize the IOMMU_INIT macros to create this dependency:

               [null]
                 |
       [pci_xen_swiotlb_detect]
                 |
       [pci_swiotlb_detect_override]
                 |
       [pci_swiotlb_detect_4gb]

In other words, we set 'pci_xen_swiotlb_detect' to be
the first detection to be run during start.

CC: Fujita Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
LKML-Reference: <1282845485-8991-7-git-send-email-konrad.wilk@oracle.com>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

arch/x86/xen/pci-swiotlb-xen.c

@@ -5,6 +5,7 @@
 
 #include <asm/xen/hypervisor.h>
 #include <xen/xen.h>
+#include <asm/iommu_table.h>
 
 int xen_swiotlb __read_mostly;
 
@@ -56,3 +57,7 @@ void __init pci_xen_swiotlb_init(void)
 		dma_ops = &xen_swiotlb_dma_ops;
 	}
 }
+IOMMU_INIT_FINISH(pci_xen_swiotlb_detect,
+		  0,
+		  pci_xen_swiotlb_init,
+		  0);