dma-mapping: fix filename references

After commit cf65a0f6f6 ("dma-mapping: move all DMA mapping code to
kernel/dma") some of the files are referring to outdated information,
i.e. old file names of DMA mapping sources. Fix it here.

Note, the lines with "Glue code for..." have been removed completely.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

arch/ia64/kernel/setup.c

@@ -256,7 +256,7 @@ __initcall(register_memory);
  * This function checks if the reserved crashkernel is allowed on the specific
  * IA64 machine flavour. Machines without an IO TLB use swiotlb and require
  * some memory below 4 GB (i.e. in 32 bit area), see the implementation of
- * lib/swiotlb.c. The hpzx1 architecture has an IO TLB but cannot use that
+ * kernel/dma/swiotlb.c. The hpzx1 architecture has an IO TLB but cannot use that
  * in kdump case. See the comment in sba_init() in sba_iommu.c.
  *
  * So, the only machvec that really supports loading the kdump kernel