unify pfn_to_page take 2 [23/25] uml funcs

Index: test-layout-free-zone/include/asm-um/page.h
===================================================================
@@ -106,9 +106,6 @@ extern unsigned long uml_physmem;
 #define __pa(virt) to_phys((void *) (unsigned long) (virt))
 #define __va(phys) to_virt((unsigned long) (phys))
 
-#define page_to_pfn(page) ((page) - mem_map)
-#define pfn_to_page(pfn) (mem_map + (pfn))
-
 #define phys_to_pfn(p) ((p) >> PAGE_SHIFT)
 #define pfn_to_phys(pfn) ((pfn) << PAGE_SHIFT)