mm/damon/vaddr: fix missing pte_unmap_unlock in damos_va_migrate_pmd_entry()

mm/damon/vaddr: fix missing pte_unmap_unlock in damos_va_migrate_pmd_entry()

If the PTE page table lock is acquired by pte_offset_map_lock(), the lock
must be released via pte_unmap_unlock().

However, in damos_va_migrate_pmd_entry(), if damos_va_filter_out() returns
true, it immediately returns without releasing the lock.

This fixes the issue by not stopping page table traversal when
damos_va_filter_out() returns true and ensuring that the lock is released.

Link: https://lkml.kernel.org/r/20251209151034.77221-1-akinobu.mita@gmail.com
Fixes: 09efc56a3b1c ("mm/damon/vaddr: consistently use only pmd_entry for damos_migrate")
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>