arch/tile: export the page_home() function.

This avois a bug in modules trying to use the function.
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

arch/tile/mm/homecache.c

@@ -394,6 +394,7 @@ int page_home(struct page *page)
 		return pte_to_home(*virt_to_pte(NULL, kva));
 	}
 }
+EXPORT_SYMBOL(page_home);
 
 void homecache_change_page_home(struct page *page, int order, int home)
 {