[vbox-dev] Fix build errors on Linux kernel version 3.2

[Larry Finger]

In Linux kernel 3.2, the iommu API changed. The following patch, copyright 2011 
by Larry Finger and released under an MIT license, allows the VirtualBox module 
vboxpci to build:

Index: vboxhost/vboxpci/linux/VBoxPci-linux.c
===================================================================
--- vboxhost.orig/vboxpci/linux/VBoxPci-linux.c
+++ vboxhost/vboxpci/linux/VBoxPci-linux.c
@@ -146,7 +146,11 @@ static int __init VBoxPciLinuxInit(void)
  #endif

  #ifdef VBOX_WITH_IOMMU
+# if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 2, 0)
+    if (iommu_present(&pci_bus_type))
+#else
      if (iommu_found())
+#endif
          printk(KERN_INFO "vboxpci: IOMMU found\n");
      else
          printk(KERN_INFO "vboxpci: IOMMU not found (not registered)\n");
@@ -984,9 +988,15 @@ int  vboxPciOsInitVm(PVBOXRAWPCIDRVVM pT
      printk(KERN_DEBUG "vboxPciOsInitVm: %p\n", pThis);
  #endif
  #ifdef VBOX_WITH_IOMMU
+# if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 2, 0)
+    if (iommu_present(&pci_bus_type))
+    {
+        pThis->pIommuDomain = iommu_domain_alloc(&pci_bus_type);
+#else
      if (iommu_found())
      {
          pThis->pIommuDomain = iommu_domain_alloc();
+#endif
          if (!pThis->pIommuDomain)
          {
              printk(KERN_DEBUG "cannot allocate IOMMU domain\n");