Clearly the intention was to enable it, as ECDSA_C was defined, but the
benchmark also requires SHA-256 for ECDSA.
Also, specify "ecdh ecdsa" when invoking the benchmark program, in order
to avoid spurious output about SHA-256.
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>