Cleanup following the removal in TF-PSA-Crypto of:
- MBEDTLS_NO_PLATFORM_ENTROPY
- MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES
- MBEDTLS_ENTROPY_HARDWARE_ALT
- MBEDTLS_ENTROPY_MIN_HARDWARE
Only MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES was still
present in Mbed TLS.
Signed-off-by: Ronald Cron <ronald.cron@arm.com>