arm64: renesas: r8a7795 dtsi: Add all HSCIF nodes

Add the device nodes for all HSCIF serial ports, incl. clocks, clock
domain, and dma properties.

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