Fix LMS function documentation

Signed-off-by: Raef Coles <raef.coles@arm.com>
diff --git a/include/mbedtls/lms.h b/include/mbedtls/lms.h
index 3e84ce0..9a8afa1 100644
--- a/include/mbedtls/lms.h
+++ b/include/mbedtls/lms.h
@@ -269,7 +269,7 @@
  * \param ctx                The initialized LMS public context to generate the key
  *                           from and store it into.
  *
- * \param ctx                The LMS private context to read the private key
+ * \param priv_ctx           The LMS private context to read the private key
  *                           from. This must have been initialized and contain a
  *                           private key.
  *