mm/swap: use helper is_swap_pte() in swap_vma_readahead

mm/swap: use helper is_swap_pte() in swap_vma_readahead

Patch series "A few cleanup patches for swap".

This series contains a few patches to fix the comment, remove unneeded
return value, use some helpers and so on.  More details can be found in
the respective changelogs.

This patch (of 14):

Use helper is_swap_pte() to check whether pte is swap entry to make code
more clear.  Minor readability improvement.

Link: https://lkml.kernel.org/r/20220509131416.17553-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20220509131416.17553-2-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Howells <dhowells@redhat.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>