arm64: dts: renesas: r8a774a1: Add PCIe device nodes

This patch adds PCIe{0,1} device nodes for R8A774A1 SoC.

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>