[TF-M] Boot seed in TFM Attestation tests

Hello,

Using a real boot seed instead of the dummy one is causing a Attestation Service regression fail. The log: Running Test Suite Initial Attestation Service non-secure interface tests(TFM_ATTEST_TEST_2XXX)...

Executing 'TFM_ATTEST_TEST_2004'

Description: 'ECDSA signature test of attest token' decode_test_normal_sig() returned: -55 Attest token decode_test_normal_sig() has failed (Failed at ../../../../../../middleware/tfm/test/suites/attestation/non_secure/attestation_ns_interface_testsuite.c:136) TEST FAILED!

Is it know issue? Probably, it's better to use a real boot seed by the Attestation tests, returned by tfm_plat_get_initial_attest_key()?

Thank you, Andrej Butok