psa: cipher: Add utility functions
psa: cipher: Add utility functions

Isolate the Mbed TLS cipher driver interfaces.
Do the actual cipher operations in utility
functions that are just called by the interface
functions.

The utility functions are intended to be also called
by the cipher test driver interface functions (to be
introduced subsequently) and allow to test the case
where cipher operations are fully accelerated with no
fallback (component test_psa_crypto_config_basic of
all.sh).

Signed-off-by: Ronald Cron <b35ff5b7ca26c4ae9b66b92f2cf34224c8e26b08@arm.com>

Mbed-TLS/mbedtls,Mbed-TLS/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,ARMmbed/mbedtls,NXPmicro/mbedtls,Mbed-TLS/mbedtls,NXPmicro/mbedtls,NXPmicro/mbedtls,NXPmicro/mbedtls,ARMmbed/mbedtls,ARMmbed/mbedtls