If setting the MBEDTLS_PLATFORM_NV_SEED_ALT and MBEDTLS_ENTROPY_NV_SEED flags and not
setting MBEDTLS_PLATFORM_NV_SEED_WRITE_MACRO and MBEDTLS_PLATFORM_NV_SEED_READ_MACRO flags
mbed-os will add an entropy source to the relevent partition - SPE in case of daul core or
in case of single core V7 to the main partition.
The defualt behaviour will be to read or write the data from the ITS.
Change error from `MBEDTLS_PLATFORM_HW_FAILED` to
`MBEDTLS_PLATFORM_HW_ACCEL_FAILED` and the value to 0x70,
as the previous value cannot be used as a low level error code.
1. Move the `mbedtls_platform_context` to be platform code, in `features/mbedtls/platfrom/`.
2. Add static refernce counter, to setup and teardown the platform code only once.
3. Adjust Cryptocell porting accordingly.
The configuration option for the mbed TLS specific hardware acceleration
has to be in the macro section and not in the device capabilities
section in targets.json.
The option has also been renamed to better reflect its function.
The crypto hardware acceleration might require defining a lot of mbed
TLS specific macros. Enumerating all of them in `targets.json` creates
too much noise, therefore we move it into a target specific mbed TLS
header.
The target with crypto hardware acceleration has to
- indicate its capability in `targets.json` by adding "CRYPTO"
to the "device_has" section
- has to define his crypto hardware acceleration related macros
in an `mbedtls_device.h` header
- place the `mbedtls_device.h` file in the
`features/mbedtls/targets/TARGET_XXXX`
directory specific to the target