Add psa_key_agreement_iop_abort() documentation

Signed-off-by: Paul Elliott <paul.elliott@arm.com>

tf-psa-crypto/core/psa_crypto_ecp.c

@@ -631,4 +631,11 @@ psa_status_t psa_key_agreement_iop_complete(
     return PSA_SUCCESS;
 }
 
+psa_status_t psa_key_agreement_iop_abort(
+    psa_key_agreement_iop_t *operation)
+{
+    (void) operation;
+
+    return PSA_SUCCESS;
+}
 #endif /* MBEDTLS_PSA_CRYPTO_C */

tf-psa-crypto/include/psa/crypto.h

@@ -5117,6 +5117,47 @@ psa_status_t psa_key_agreement_iop_complete(
     psa_key_agreement_iop_t *operation,
     psa_key_id_t *key);
 
+/**
+ * \brief                       Abort a key agreement operation.
+ *
+ * \warning                     This is a beta API, and thus subject to change
+ *                              at any point. It is not bound by the usual
+ *                              interface stability promises.
+ *
+ * \note                        This function is the only function that clears
+ *                              the number of ops completed as part of the
+ *                              operation. Please ensure you copy this value via
+ *                              \c psa_key_agreement_iop_get_num_ops() if
+ *                              required before calling.
+ *
+ * \note                        Aborting an operation frees all
+ *                              associated resources except for the operation
+ *                              structure itself. Once aborted, the operation
+ *                              object can be reused for another operation by
+ *                              calling \c psa_key_agreement_iop_setup() again.
+ *
+ * \note                        You may call this function any time after the
+ *                              operation object has been initialized.
+ *                              In particular, calling \c
+ *                              psa_key_agreement_iop_abort() after the
+ *                              operation has already been terminated by a call
+ *                              to \c psa_key_agreement_iop_abort() or
+ *                              psa_key_agreement_iop_complete() is safe.
+ *
+ * \param[in,out] operation     The \c psa_key_agreement_iop_t to use
+ *
+ * \retval #PSA_SUCCESS
+ *          The operation was aborted successfully.
+ *
+ * \retval #PSA_ERROR_NOT_SUPPORTED \emptydescription
+ * \retval #PSA_ERROR_BAD_STATE
+ *          The library has not been previously initialized by
+ *          \c psa_crypto_init(). It is implementation-dependent whether a
+ *          failure to initialize results in this error code.
+ */
+psa_status_t psa_key_agreement_iop_abort(
+    psa_key_agreement_iop_t *operation);
+
 /**@}*/
 
 #ifdef __cplusplus