The support for the PSA crypto driver interface
is not optional anymore as the implementation of
the PSA cryptography interface has been restructured
around the PSA crypto driver interface (see
psa-crypto-implementation-structure.md). There is
thus no purpose for the configuration options
MBEDTLS_PSA_CRYPTO_DRIVERS anymore.
Signed-off-by: Ronald Cron <ronald.cron@arm.com>