x86: fix warning in e820_reserve_resources with 32bit

when 64bit resource is not enabled, we get:

arch/x86/kernel/e820.c: In function ‘e820_reserve_resources’:
arch/x86/kernel/e820.c:1217: warning: comparison is always false due to limited range of data type

because res->start/end is resource_t aka u32. it will overflow.

fix it with temp end of u64

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/e820.c

@@ -1202,6 +1202,7 @@ void __init e820_reserve_resources(void)
 {
 	int i;
 	struct resource *res;
+	u64 end;
 
 	res = alloc_bootmem_low(sizeof(struct resource) * e820.nr_map);
 	for (i = 0; i < e820.nr_map; i++) {
@@ -1211,14 +1212,16 @@ void __init e820_reserve_resources(void)
 		case E820_NVS:	res->name = "ACPI Non-volatile Storage"; break;
 		default:	res->name = "reserved";
 		}
-		res->start = e820.map[i].addr;
-		res->end = res->start + e820.map[i].size - 1;
+		end = e820.map[i].addr + e820.map[i].size - 1;
 #ifndef CONFIG_RESOURCES_64BIT
-		if (res->end > 0x100000000ULL) {
+		if (end > 0x100000000ULL) {
 			res++;
 			continue;
 		}
 #endif
+		res->start = e820.map[i].addr;
+		res->end = end;
+
 		res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
 		insert_resource(&iomem_resource, res);
 		res++;