Platform/RPi: Set SD routing according to model

The Raspberry Pi 4 has a new SD controller. As a result we must
handle SD routing according to the model, which we perform in
the Config driver by using the GetModelFamily () call that was
recently introduced.

Signed-off-by: Pete Batard <pete@akeo.ie>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>