BACKPORT: FROMLIST: arm64: mte: Simplify swap tag restoration logic

As a result of the previous two patches, there are no circumstances
in which a swapped-in page is installed in a page table without first
having arch_swap_restore() called on it. Therefore, we no longer need
the logic in set_pte_at() that restores the tags, so remove it.

Signed-off-by: Peter Collingbourne <pcc@google.com>
Link: https://linux-review.googlesource.com/id/I8ad54476f3b2d0144ccd8ce0c1d7a2963e5ff6f3


Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/all/20230523004312.1807357-4-pcc@google.com/
Change-Id: I8ad54476f3b2d0144ccd8ce0c1d7a2963e5ff6f3
[pcc: resolved merge conflict]
Bug: 274890466