thermal/drivers/bcm2711: Don't clamp temperature at zero

thermal/drivers/bcm2711: Don't clamp temperature at zero

The thermal sensor on BCM2711 is capable of negative temperatures, so don't
clamp the measurements at zero. Since this was the only use for variable t,
drop it.

This change based on a patch by Dom Cobley, who also tested the fix.

Fixes: f63c807f2e9e ("thermal: Add BCM2711 thermal driver")
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20220412195423.104511-1-stefan.wahren@i2se.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>