docs(auth): add missing AUTH_PARAM_NV_CTR value

Section "Describing the authentication method(s)" of the Authentication
Framework documentation shows the authentication parameters types
(auth_param_type_t enum type) but is missing the AUTH_PARAM_NV_CTR
value. Add it.

Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
Change-Id: I7c9022badfb039bfa9f999ecee40f18b49e6764c
diff --git a/docs/design/auth-framework.rst b/docs/design/auth-framework.rst
index a5ca377..6dc2245 100644
--- a/docs/design/auth-framework.rst
+++ b/docs/design/auth-framework.rst
@@ -505,11 +505,12 @@
 
     typedef enum {
         AUTH_PARAM_NONE,
-        AUTH_PARAM_RAW_DATA,        /* Raw image data */
+        AUTH_PARAM_RAW_DATA,    /* Raw image data */
         AUTH_PARAM_SIG,         /* The image signature */
         AUTH_PARAM_SIG_ALG,     /* The image signature algorithm */
         AUTH_PARAM_HASH,        /* A hash (including the algorithm) */
         AUTH_PARAM_PUB_KEY,     /* A public key */
+        AUTH_PARAM_NV_CTR,      /* A non-volatile counter */
     } auth_param_type_t;
 
 The AM defines the following structure to identify an authentication parameter