mm: Move lowmem_page_address() a little later

LoongArch will override page_to_virt() which use page_address() in the
KFENCE case (by defining WANT_PAGE_VIRTUAL/HASHED_PAGE_VIRTUAL). So move
lowmem_page_address() a little later to avoid such build errors:

error: implicit declaration of function 'page_address'.
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

include/linux/mm.h

@@ -2207,11 +2207,6 @@ static inline int arch_make_folio_accessible(struct folio *folio)
  */
 #include <linux/vmstat.h>
 
-static __always_inline void *lowmem_page_address(const struct page *page)
-{
-	return page_to_virt(page);
-}
-
 #if defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL)
 #define HASHED_PAGE_VIRTUAL
 #endif
@@ -2234,6 +2229,11 @@ void set_page_address(struct page *page, void *virtual);
 void page_address_init(void);
 #endif
 
+static __always_inline void *lowmem_page_address(const struct page *page)
+{
+	return page_to_virt(page);
+}
+
 #if !defined(HASHED_PAGE_VIRTUAL) && !defined(WANT_PAGE_VIRTUAL)
 #define page_address(page) lowmem_page_address(page)
 #define set_page_address(page, address)  do { } while(0)