thermal: brcmstb_thermal: Do not use DT coefficients

At the time the brcmstb_thermal driver and its binding were merged, the
DT binding did not make the coefficients properties a mandatory one,
therefore all users of the brcmstb_thermal driver out there have a non
functional implementation with zero coefficients. Even if these
properties were provided, the formula used for computation is incorrect.

The coefficients are entirely process specific (right now, only 28nm is
supported) and not board or SoC specific, it is therefore appropriate to
hard code them in the driver given the compatibility string we are
probed with which has to be updated whenever a new process is
introduced.

We remove the existing coefficients definition since subsequent patches
are going to add support for a new process and will introduce new
coefficients as well.

Fixes: 9e03cf1b

 ("thermal: add brcmstb AVS TMON driver")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200114190607.29339-2-f.fainelli@gmail.com