PSA PAKE: improve and fix documentation

Signed-off-by: Janos Follath <janos.follath@arm.com>
diff --git a/include/psa/crypto_sizes.h b/include/psa/crypto_sizes.h
index d8fc997..a603c9d 100644
--- a/include/psa/crypto_sizes.h
+++ b/include/psa/crypto_sizes.h
@@ -1143,7 +1143,8 @@
  *
  * \param alg           A PAKE algorithm (PSA_ALG_XXX value such that
  *                      #PSA_ALG_IS_PAKE(\p alg) is true).
- * \param primitive     A primitive that is compatible with algorithm \p alg.
+ * \param primitive     A primitive of type ::psa_pake_primitive_t that is
+ *                      compatible with algorithm \p alg.
  * \param output_step   A value of type ::psa_pake_step_t that is valid for the
  *                      algorithm \p alg.
  * \return              A sufficient output buffer size for the specified