thp: remove HPAGE_PMD_ORDER minimum assertion

We now handle order-1 folios correctly, so we don't need this assertion
any more.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: Matthew Wilcox (Oracle)

mm/huge_memory.c

@@ -740,11 +740,6 @@ static int __init hugepage_init(void)
 	 * hugepages can't be allocated by the buddy allocator
 	 */
 	MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER > MAX_PAGE_ORDER);
-	/*
-	 * we use page->mapping and page->index in second tail page
-	 * as list_head: assuming THP order >= 2
-	 */
-	MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
 
 	err = hugepage_init_sysfs(&hugepage_kobj);
 	if (err)