When MBEDTLS_PSA_INJECT_ENTROPY is enabled, we disable standard entropy
sources, so mbedtls_entropy_func() doesn't work out of the box. Disable
tests that rely on it. MBEDTLS_PSA_INJECT_ENTROPY is intended for PSA-only
environments anyway, so it doesn't matter if some legacy features don't work
normally.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>