mm/huge_memory: update file PMD counter before folio_put()

In the Linux kernel, the following vulnerability has been resolved: mm/huge_memory: update file PMD counter before folio_put() __split_huge_pmd_locked() updates the file/shmem RSS counter after dropping the PMD mapping's folio reference. If folio_put() drops the last reference, mm_counter_file() can later read freed folio state via folio_test_swapbacked(). Move the counter update before folio_put().