Add MBEDTLS_LMS_PRIVATE define

To enable private key operations

Signed-off-by: Raef Coles <raef.coles@arm.com>
diff --git a/include/mbedtls/mbedtls_config.h b/include/mbedtls/mbedtls_config.h
index 8c833b1..c0caf75 100644
--- a/include/mbedtls/mbedtls_config.h
+++ b/include/mbedtls/mbedtls_config.h
@@ -2469,13 +2469,25 @@
  * Module:  library/lms.c
  * Caller:
  *
- * Requires: MBEDTLS_MD_C
+ * Requires: MBEDTLS_PSA_CRYPTO_C
  *
- * Uncomment to enable the LMS signature algorithm.
+ * Uncomment to enable the LMS verification algorithm and public key operations.
  */
 #define MBEDTLS_LMS_C
 
 /**
+ * \def MBEDTLS_LMS_PRIVATE
+ *
+ * Enable LMS private-key operations and signing code. Functions enabled by this
+ * option are experimental, and should not be used in production.
+ *
+ * Requires: MBEDTLS_LMS_C
+ *
+ * Uncomment to enable the LMS signature algorithm and private key operations.
+ */
+// #define MBEDTLS_LMS_PRIVATE
+
+/**
  * \def MBEDTLS_NIST_KW_C
  *
  * Enable the Key Wrapping mode for 128-bit block ciphers,