Update vCPU link after refactor.

Bug: 144898870
Change-Id: I293942d90c0f92010810faf4f0595f5a91bc4ca8
diff --git a/docs/Architecture.md b/docs/Architecture.md
index 461d51f..e0261d8 100644
--- a/docs/Architecture.md
+++ b/docs/Architecture.md
@@ -84,7 +84,7 @@
 *   Some internal state maintained by Hafnium (locks, mailbox wait lists,
     mailbox state, log buffer).
 
-Each [vCPU](../inc/hf/cpu.h) also has:
+Each [vCPU](../inc/hf/vcpu.h) also has:
 
 *   A set of saved registers, for when it isn't being run on a physical CPU.
 *   A current state (switched off, ready to run, running, waiting for a message