x86/iommu: Use NULL instead of plain 0 for __IOMMU_INIT

IOMMU_INIT_POST and IOMMU_INIT_POST_FINISH pass the plain value
0 instead of NULL to __IOMMU_INIT. Fix this and make sparse
happy by doing so.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: Joerg Roedel <joerg.roedel@amd.com>
Link: http://lkml.kernel.org/r/1346621506-30857-8-git-send-email-minipli@googlemail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/iommu_table.h

@@ -63,10 +63,10 @@ struct iommu_table_entry {
  * to stop detecting the other IOMMUs after yours has been detected.
  */
 #define IOMMU_INIT_POST(_detect)					\
-	__IOMMU_INIT(_detect, pci_swiotlb_detect_4gb,  0, 0, 0)
+	__IOMMU_INIT(_detect, pci_swiotlb_detect_4gb,  NULL, NULL, 0)
 
 #define IOMMU_INIT_POST_FINISH(detect)					\
-	__IOMMU_INIT(_detect, pci_swiotlb_detect_4gb,  0, 0, 1)
+	__IOMMU_INIT(_detect, pci_swiotlb_detect_4gb,  NULL, NULL, 1)
 
 /*
  * A more sophisticated version of IOMMU_INIT. This variant requires: