remove FreeRTOS and arch/armv8a dependencies for renesas/rcar platform

Rcar product currently has dependencies on both FreeRTOS and armv8a architecture, the goal of this merge request is to remove these dependencies.

Renesas Salvator platform is using CortexA53 core, that seems unsupported for the moment in arch/aarch64. So I have added the CortexA53 support in arch/arm/aarch64/ files.

Also on Salvator platform, the core running the SCP firmware is not the primary core of the cluster. So the following code (on file 'arch/arm/aarch64/src/arch_crt0.S') should be updated to be less restrictive (by updating the mask 0xffffff for example):

    /* Ensure primary core */
    mrs x0, mpidr_el1
    and x0, x0, #0xffffff
    cbnz x0, wfe_loop

Is it something possible, or is there any strong limitations on other platforms?

Signed-off-by: Florian Sylvestre fsylvestre@baylibre.com Signed-off-by: Nicolas Royer nroyer@nanog.fr