rpi3: Enable network support and ssh related packages

Added the additional packages needed for network and ssh support
to be included in the root file system for rpi3 platform.

Link: https://github.com/OP-TEE/optee_client/issues/234


Signed-off-by: Jayanth Dodderi Chidanand <jayanthchidanand94@gmail.com>
Reviewed-by: Joakim Bech <joakim.bech@linaro.org>
Acked-by: Etienne Carriere <etienne.carriere@linaro.org>