clk: renesas: r8a779a0: Add SYS-DMAC clocks

Add the module clocks used by the Direct Memory Access Controller for
System (SYS-DMAC) instances on the Renesas R-Car V3U (r8a779a0) SoC.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20210107180109.1946475-1-geert+renesas@glider.be