fix(docs): add backticks to fix Markdown formatting

Change-Id: I479da776c2ba471debea2b7257d10cf90be81a1e
Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
diff --git a/docs/VmInterface.md b/docs/VmInterface.md
index f061ebc..63f5e60 100644
--- a/docs/VmInterface.md
+++ b/docs/VmInterface.md
@@ -31,26 +31,26 @@
 The primary VM will be able to control the physical CPUs through the following
 PSCI 1.1 calls, which will be forwarded to the underlying implementation in EL3:
 
-*   PSCI_VERSION
-*   PSCI_FEATURES
-*   PSCI_SYSTEM_OFF
-*   PSCI_SYSTEM_RESET
-*   PSCI_AFFINITY_INFO
-*   PSCI_CPU_SUSPEND
-*   PSCI_CPU_OFF
-*   PSCI_CPU_ON
+*   `PSCI_VERSION`
+*   `PSCI_FEATURES`
+*   `PSCI_SYSTEM_OFF`
+*   `PSCI_SYSTEM_RESET`
+*   `PSCI_AFFINITY_INFO`
+*   `PSCI_CPU_SUSPEND`
+*   `PSCI_CPU_OFF`
+*   `PSCI_CPU_ON`
 
 All other PSCI calls are unsupported.
 
 Secondary VMs will be able to control their vCPUs through the following PSCI 1.1
 calls, which will be implemented by Hafnium:
 
-*   PSCI_VERSION
-*   PSCI_FEATURES
-*   PSCI_AFFINITY_INFO
-*   PSCI_CPU_SUSPEND
-*   PSCI_CPU_OFF
-*   PSCI_CPU_ON
+*   `PSCI_VERSION`
+*   `PSCI_FEATURES`
+*   `PSCI_AFFINITY_INFO`
+*   `PSCI_CPU_SUSPEND`
+*   `PSCI_CPU_OFF`
+*   `PSCI_CPU_ON`
 
 All other PSCI calls are unsupported.