Add test case for ecdh_calc_secret

Add a test case for doing an ECDH calculation by calling
mbedtls_ecdh_get_params on both keys, then mbedtls_ecdh_calc_secret.
diff --git a/tests/suites/test_suite_ecdh.data b/tests/suites/test_suite_ecdh.data
index fe24ed4..f90d88d 100644
--- a/tests/suites/test_suite_ecdh.data
+++ b/tests/suites/test_suite_ecdh.data
@@ -79,3 +79,11 @@
 ECDH exchange legacy context
 depends_on:MBEDTLS_ECP_DP_SECP192R1_ENABLED
 ecdh_exchange_legacy:MBEDTLS_ECP_DP_SECP192R1
+
+ECDH calc_secret: ours first, SECP256R1 (RFC 5903)
+depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED
+ecdh_exchange_calc_secret:MBEDTLS_ECP_DP_SECP256R1:"c6ef9c5d78ae012a011164acb397ce2088685d8f06bf9be0b283ab46476bee53":"04dad0b65394221cf9b051e1feca5787d098dfe637fc90b9ef945d0c37725811805271a0461cdb8252d61f1c456fa3e59ab1f45b33accf5f58389e0577b8990bb3":0:"d6840f6b42f6edafd13116e0e12565202fef8e9ece7dce03812464d04b9442de"
+
+ECDH calc_secret: theirs first, SECP256R1 (RFC 5903)
+depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED
+ecdh_exchange_calc_secret:MBEDTLS_ECP_DP_SECP256R1:"c6ef9c5d78ae012a011164acb397ce2088685d8f06bf9be0b283ab46476bee53":"04dad0b65394221cf9b051e1feca5787d098dfe637fc90b9ef945d0c37725811805271a0461cdb8252d61f1c456fa3e59ab1f45b33accf5f58389e0577b8990bb3":1:"d6840f6b42f6edafd13116e0e12565202fef8e9ece7dce03812464d04b9442de"