thermal: Add BCM2711 thermal driver

This adds the thermal sensor driver for the Broadcom BCM2711 SoC,
which is placed on the Raspberry Pi 4. The driver only provides
SoC temperature reading so far.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Tested-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/1578941778-23321-3-git-send-email-stefan.wahren@i2se.com