rcar: add rcar platform

This patch adds support for the rcar platform running on FreeRTOS.
FreeRTOS source code is temporarily included into rcar product directory
until armv8-a support is added to CMSIS-FreeRTOS repository.

Change-Id: Ia828f903d52df236922fe7f6f548bce06ee131cc
Signed-off-by: Tsutomu Muroya <tsutomu.muroya.jy@bp.renesas.com>
Signed-off-by: Nicolas Royer <nroyer@baylibre.com>