arm64: dts: renesas: r8a77995: Use r8a7795-sysc binding definitions

Replace the hardcoded power domain indices by R8A77995_PD_* symbols.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>