PSA PBKDF2: add new key types

Question to reviewers: regarding the numeric values, I'm not sure I've
incremented the right byte/nibble. Should this be 0x1201, 0x1202
instead, or something else? Is there a convention I should be aware of?

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/include/psa/crypto_values.h b/include/psa/crypto_values.h
index 5e865c9..2c247d0 100644
--- a/include/psa/crypto_values.h
+++ b/include/psa/crypto_values.h
@@ -414,6 +414,20 @@
  */
 #define PSA_KEY_TYPE_DERIVE                         ((psa_key_type_t)0x1200)
 
+/** A low-entropy secret for password hashing or key derivation.
+ *
+ * The key policy determines which key derivation algorithm the key
+ * can be used for.
+ */
+#define PSA_KEY_TYPE_PASSWORD                       ((psa_key_type_t)0x1300)
+
+/** A secret value that can be mixed in when doing password hashing.
+ *
+ * The key policy determines which key derivation algorithm the key
+ * can be used for.
+ */
+#define PSA_KEY_TYPE_PEPPER                         ((psa_key_type_t)0x1400)
+
 /** Key for a cipher, AEAD or MAC algorithm based on the AES block cipher.
  *
  * The size of the key can be 16 bytes (AES-128), 24 bytes (AES-192) or