Simplify mbedtls_ssl_get_base_mode
Simplify mbedtls_ssl_get_base_mode

Reduce the amount of ifdef's by making the USE_PSA_CRYPTO and
non-USE_PSA_CRYPTO definitions independent.

No behavior change.

Signed-off-by: Gilles Peskine <f805f64266d288fc5467baa7be6cd0ff366f477b@arm.com>

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