Pull arm64 fix from Will Deacon:
 "We received a report this week that the generic version of
  pfn_valid(), which we switched to this merge window in 16c9afc77660
  ("arm64/mm: drop HAVE_ARCH_PFN_VALID"), interacts badly with
  dma_map_resource() due to the following check:

        /* Don't allow RAM to be mapped */
        if (WARN_ON_ONCE(pfn_valid(PHYS_PFN(phys_addr))))
                return DMA_MAPPING_ERROR;

  Since the ongoing saga to determine the semantics of pfn_valid() is
  unlikely to be resolved this week (does it indicate valid memory, or
  just the presence of a struct page, or whether that struct page has
  been initialised?), just revert back to our old version of pfn_valid()
  for 5.14.

  Summary:

   - Fix dma_map_resource() by reverting back to old pfn_valid() code"

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  Partially revert "arm64/mm: drop HAVE_ARCH_PFN_VALID"