encrypted-keys: fixed valid_master_desc() function description

Valid key type prefixes for the parameter 'key-type' are: 'trusted' and
'user'.
Signed-off-by: Roberto Sassu <roberto.sassu@polito.it>
Acked-by: Gianluca Ramunno <ramunno@polito.it>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

security/keys/encrypted.c

@@ -84,7 +84,7 @@ static int aes_get_sizes(void)
 /*
  * valid_master_desc - verify the 'key-type:desc' of a new/updated master-key
  *
- * key-type:= "trusted:" | "encrypted:"
+ * key-type:= "trusted:" | "user:"
  * desc:= master-key description
  *
  * Verify that 'key-type' is valid and that 'desc' exists. On key update,