mm/mincore: handle non-swap entries before !CONFIG_SWAP guard

mm/mincore: handle non-swap entries before !CONFIG_SWAP guard

mincore_swap() also fields migration/hwpoison entries (and shmem
swapin-error entries), which can exist on !CONFIG_SWAP builds when
CONFIG_MIGRATION or CONFIG_MEMORY_FAILURE is enabled.  The
!IS_ENABLED(CONFIG_SWAP) guard ran before the non-swap-entry early return,
so mincore_pte_range() can spuriously WARN and report these pages
nonresident on !CONFIG_SWAP kernels.

Move the guard below the non-swap-entry check so only true swap entries
trip the WARN, and migration/hwpoison entries take the existing "uptodate
/ non-shmem" path.

Link: https://lore.kernel.org/20260602172247.279421-1-usama.arif@linux.dev
Fixes: 1f2052755c15 ("mm/mincore: use a helper for checking the swap cache")
Signed-off-by: Usama Arif <usama.arif@linux.dev>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: Chris Li <chrisl@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>