dt-bindings: can: rcar_can: Fix RZ/G2 CAN clocks

According to the latest information, the clock options for CAN on RZ/G2
are the same as the ones available on R-Car Gen3

Fixes: 868b7c0f ("dt-bindings: can: rcar_can: Add r8a774a1 support")
Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Chris Paterson <Chris.Paterson2@renesas.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>