thermal/drivers: Add TSU driver for RZ/G2L

thermal/drivers: Add TSU driver for RZ/G2L

The RZ/G2L SoC incorporates a thermal sensor unit (TSU) that measures the
temperature inside the LSI.

The thermal sensor in this unit measures temperatures in the range from
−40 degree Celsius to 125 degree Celsius with an accuracy of ±3°C. The
TSU repeats measurement at 20 microseconds intervals and automatically
updates the results of measurement.

The TSU has no interrupts as well as no external pins.

This patch adds Thermal Sensor Unit(TSU) driver for RZ/G2L SoC.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Link: https://lore.kernel.org/r/20211130155757.17837-3-biju.das.jz@bp.renesas.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>