arm64: dts: renesas: r8a774c0-cat874: Add pciec0 support

Silicon Linux CAT 874 board has 2GB DDR memory. Update the dma-ranges
mapping for pciec0 node. Also declare pcie bus clock, since it is
generated on the CAT874 main board.

Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>