Add modulus to parameter ordering

Signed-off-by: Werner Lewis <werner.lewis@arm.com>
diff --git a/library/bignum_mod_raw.h b/library/bignum_mod_raw.h
index ddb2d09..93df46f 100644
--- a/library/bignum_mod_raw.h
+++ b/library/bignum_mod_raw.h
@@ -36,7 +36,8 @@
  *   specified by the \p int_rep field of the modulus for arithmetic
  *   functions. Utility functions may allow for different representation.
  * - **Parameter ordering**: for bignum parameters, outputs come before inputs.
- *   Temporaries come last.
+ *   The modulus is passed after other bignum input parameters. Temporaries
+ *   come last.
  * - **Aliasing**: in general, output bignums may be aliased to one or more
  *   inputs. Modulus values may not be aliased to any other parameter. Outputs
  *   may not be aliased to one another. Temporaries may not be aliased to any