x86: change aper valid checking sequence

old sequence:
  size ==> >4G  ==> point to RAM

changed to:
  >4G ==> point to RAM ==> size

some bios even leave aper to unclear, so check size at last.

To avoid reporting:

  Node 0: Aperture @ 4a42000000 size 32 MB
  Aperture too small (32 MB)

with this change we will get:

  Node 0: Aperture @ 4a42000000 size 32 MB
  Aperture beyond 4G. Ignoring.
Signed-off-by: NYinghai Lu <yinghai.lu@sun.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/aperture_64.c

@@ -85,10 +85,6 @@ static int __init aperture_valid(u64 aper_base, u32 aper_size)
 	if (!aper_base)
 		return 0;
 
-	if (aper_size < 64*1024*1024) {
-		printk(KERN_ERR "Aperture too small (%d MB)\n", aper_size>>20);
-		return 0;
-	}
 	if (aper_base + aper_size > 0x100000000UL) {
 		printk(KERN_ERR "Aperture beyond 4GB. Ignoring.\n");
 		return 0;
@@ -97,6 +93,10 @@ static int __init aperture_valid(u64 aper_base, u32 aper_size)
 		printk(KERN_ERR "Aperture pointing to e820 RAM. Ignoring.\n");
 		return 0;
 	}
+	if (aper_size < 64*1024*1024) {
+		printk(KERN_ERR "Aperture too small (%d MB)\n", aper_size>>20);
+		return 0;
+	}
 
 	return 1;
 }