iommu/amd: Remove obsolete comment

The AMD IOMMU driver only uses the page-sizes it gets from
IOMMU core and uses the appropriate page-size. So this
comment is not necessary.
Signed-off-by: Joerg Roedel <joro@8bytes.org>

drivers/iommu/amd_iommu.c

@@ -57,16 +57,6 @@
  * physically contiguous memory regions it is mapping into page sizes
  * that we support.
  *
- * Traditionally the IOMMU core just handed us the mappings directly,
- * after making sure the size is an order of a 4KiB page and that the
- * mapping has natural alignment.
- *
- * To retain this behavior, we currently advertise that we support
- * all page sizes that are an order of 4KiB.
- *
- * If at some point we'd like to utilize the IOMMU core's new behavior,
- * we could change this to advertise the real page sizes we support.
- *
  * 512GB Pages are not supported due to a hardware bug
  */
 #define AMD_IOMMU_PGSIZES	((~0xFFFUL) & ~(2ULL << 38))