Clarify IOP key generation restriction

Public keys can't be generated.

Co-authored-by: Gilles Peskine <gilles.peskine@arm.com>
Signed-off-by: Janos Follath <janos.follath@arm.com>
diff --git a/tf-psa-crypto/include/psa/crypto.h b/tf-psa-crypto/include/psa/crypto.h
index 5d40d07..77b7407 100644
--- a/tf-psa-crypto/include/psa/crypto.h
+++ b/tf-psa-crypto/include/psa/crypto.h
@@ -5272,7 +5272,7 @@
  *                              aborted by calling \c
  *                              psa_generate_key_iop_abort().
  *
- * \note                        Only asymmetric keys are supported. (See \p attributes.)
+ * \note                        Only asymmetric key pairs are supported. (See \p attributes.)
  *
  * \param[in, out] operation    The \c psa_generate_key_iop_t to use.
  *                              This must be initialized as per the