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

In the Linux kernel, the following vulnerability has been resolved:

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.