arm64: mte: Sync tags for pages where PTE is untagged

arm64: mte: Sync tags for pages where PTE is untagged

A KVM guest could store tags in a page even if the VMM hasn't mapped
the page with PROT_MTE. So when restoring pages from swap we will
need to check to see if there are any saved tags even if !pte_tagged().

However don't check pages for which pte_access_permitted() returns false
as these will not have been swapped out.

Reviewed-by: Catalin Marinas <[email protected]>
Signed-off-by: Steven Price <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>
Link: https://lore.kernel.org/r/[email protected]