[REFACTOR] Hafnium style: capitalize CPU, vCPU, and VM.

Change-Id: I6090deee0f52737653f5b18c09a1c64cadd38c8c
diff --git a/src/vm.c b/src/vm.c
index 856509f..0f36e21 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -100,7 +100,7 @@
 }
 
 /**
- * Locks the given VM and updates `locked` to hold the newly locked vm.
+ * Locks the given VM and updates `locked` to hold the newly locked VM.
  */
 struct vm_locked vm_lock(struct vm *vm)
 {