soc: renesas: r8a77970-sysc: Remove non-existent CR7 power domain

soc: renesas: r8a77970-sysc: Remove non-existent CR7 power domain

The R-Car Gen3 HardWare Manual Errata for Rev. 0.80 (Feb 28, 2018)
removed the CR7 power domain on R-Car V3M, as this SoC does not have an
ARM Cortex-R7 Realtime Core.

As this definition was never used from DT, it can just be removed.

Fixes: 833bdb47c826a1a6 ("dt-bindings: power: add R8A77970 SYSC power domain definitions")
Fixes: bab9b2a74fe9da96 ("soc: renesas: rcar-sysc: add R8A77970 support")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>