arm64: dts: renesas: r8a774c0: Add clkp2 clock to CAN nodes

According to the latest information, clkp2 is available on RZ/G2.
Modify CAN0 and CAN1 nodes accordingly.

Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Chris Paterson <Chris.Paterson2@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>