vm header update to make it ascii file

This file is causing license header checker to fail because
it contains unicode characters. Remove the characters to
change it back to a pure ascii file.

Change-Id: I92bfb02812b214886b60c6f466da1e96ee8928ae
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
diff --git a/inc/hf/vm.h b/inc/hf/vm.h
index 0e4d23f..75974cf 100644
--- a/inc/hf/vm.h
+++ b/inc/hf/vm.h
@@ -26,11 +26,11 @@
  * The state of an RX buffer.
  *
  * EMPTY is the initial state. The follow state transitions are possible:
- * * EMPTY → RECEIVED: message sent to the VM.
- * * RECEIVED → READ: secondary VM returns from FFA_MSG_WAIT or
+ * * EMPTY => RECEIVED: message sent to the VM.
+ * * RECEIVED => READ: secondary VM returns from FFA_MSG_WAIT or
  *   FFA_MSG_POLL, or primary VM returns from FFA_RUN with an FFA_MSG_SEND
  *   where the receiver is itself.
- * * READ → EMPTY: VM called FFA_RX_RELEASE.
+ * * READ => EMPTY: VM called FFA_RX_RELEASE.
  */
 enum mailbox_state {
 	/** There is no message in the mailbox. */