Update vboot_reference to resolve kernel munging issue

Futility does some munging of the kernel data if the arch is x86 or
amd64, and this breaks booting through the kernel's EFI boot
stub. Futility has now been updated to not do that munging if the kernel
has the EFI boot stub enabled, so in gen_disk we can now pass in
arch=amd64, resolving a long-standing todo.

BUG=b:238316304
TEST=cargo xtask setup <image>
TEST=cargo xtask check
TEST=cargo xtask update-disk
TEST=cargo xtask qemu
TEST=cargo xtask qemu --ia32

Change-Id: I87de9dd20432e2f6c88265f3f891156996311122
Reviewed-on: https://chromium-review.googlesource.com/c/crdyboot/+/3908289
Tested-by: Nicholas Bishop <nicholasbishop@google.com>
Reviewed-by: Jeffery Miller <jefferymiller@google.com>
Auto-Submit: Nicholas Bishop <nicholasbishop@google.com>
Commit-Queue: Jeffery Miller <jefferymiller@google.com>

diff --git a/third_party/vboot_reference b/third_party/vboot_reference
index 3bd3510..956c2ef 160000
--- a/third_party/vboot_reference
+++ b/third_party/vboot_reference

@@ -1 +1 @@
-Subproject commit 3bd35108579db497b006b81e77794739b5118592
+Subproject commit 956c2efb0af310a3089b362fdb5d5f70238758f2

diff --git a/xtask/src/gen_disk.rs b/xtask/src/gen_disk.rs
index 4cb11b2..8bd7353 100644
--- a/xtask/src/gen_disk.rs
+++ b/xtask/src/gen_disk.rs

@@ -472,10 +472,7 @@
         "--vmlinuz", vmlinuz.as_str(),
         "--bootloader", bootloader.as_str(),
         "--config", config.as_str(),
-        // TODO: the kernel is actually amd64, but pass in
-        // arm64 so that vbutil won't do all the kernel
-        // munging stuff it wants to.
-        "--arch", "arm64"]).run()?;
+        "--arch", "amd64"]).run()?;
 
     // Verify it.
     Command::with_args(