x86: EFI: fix use of unitialized variable and the cache logic

Andi Kleen pointed out that the cache attribute logic is reverse in
efi_enter_virtual_mode(). This problem alone is harmless as we do not
(yet) do cache attribute conflict resolution. (This bug was not present
in the original EFI submission - I introduced it while fixing up rejects.)

While reviewing this code I noticed a second, worse problem: the use of
uninitialized md->virt_addr.

Fix both problems.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/efi.c

@@ -428,9 +428,6 @@ void __init efi_enter_virtual_mode(void)
 		else
 			va = efi_ioremap(md->phys_addr, size);
 
-		if (md->attribute & EFI_MEMORY_WB)
-			set_memory_uc(md->virt_addr, size);
-
 		md->virt_addr = (u64) (unsigned long) va;
 
 		if (!va) {
@@ -439,6 +436,9 @@ void __init efi_enter_virtual_mode(void)
 			continue;
 		}
 
+		if (!(md->attribute & EFI_MEMORY_WB))
+			set_memory_uc(md->virt_addr, size);
+
 		systab = (u64) (unsigned long) efi_phys.systab;
 		if (md->phys_addr <= systab && systab < end) {
 			systab += md->virt_addr - md->phys_addr;