mbedtls_pk_ec() is not an ideal function because:
- it provides direct access to the ecp_keypair structure wrapped
by the pk_context and
- this bypasses the PK module's control
However, since for backward compatibility, it cannot be deprecated
immediately, 2 alternative internal functions are proposed.
As a consequence:
- when ECP_C is defined, then the legacy mbedtls_pk_ec is available
- when only ECP_LIGHT is defined, but ECP_C is not, then only the
new internal functions will be available
Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
