clk: renesas: r8a779h0: Add thermal clock

Add the module clock used by the Thermal Sensor/Chip Internal Voltage
Monitor/Core Voltage Monitor (THS/CIVM/CVM) on the Renesas R-Car V4M
(R8A779H0) SoC.

Based on a patch in the BSP by Cong Dang.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://lore.kernel.org/r/befac3e8342cd552f580d34be863ef84403c541f.1709722056.git.geert+renesas@glider.be