x86: clean up max_pfn_mapped usage - 64-bit

on 64-bit we only get valid max_pfn_mapped after init_memory_mapping().

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/setup_64.c b/arch/x86/kernel/setup_64.c
index 978a0d6..2599b27 100644
--- a/arch/x86/kernel/setup_64.c
+++ b/arch/x86/kernel/setup_64.c
@@ -396,7 +396,7 @@
 
 	check_efer();
 
-	max_pfn_mapped = init_memory_mapping(0, (max_pfn_mapped << PAGE_SHIFT));
+	max_pfn_mapped = init_memory_mapping(0, (end_pfn << PAGE_SHIFT));
 	if (efi_enabled)
 		efi_init();