soc: renesas: rz-sysc: Move RZ/V2H SoC detection to the SYS driver

soc: renesas: rz-sysc: Move RZ/V2H SoC detection to the SYS driver

As per the other SoC variant of the same family, the system controller
provides SoC ID in its own registers.

Signed-off-by: John Madieu <john.madieu.xa@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/20250128031342.52675-5-john.madieu.xa@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>