thermal: rcar_gen3_thermal: Do not shadow thcode variable

The function rcar_gen3_thermal_calc_coefs() takes an argument called
'thcode' which shadows the static global 'thcode' variable. This is not
harmful but bad for readability and is harmful for planned changes to
the driver. The THCODE values should be read from hardware fuses if they
are available and only fallback to the global 'thcode' variable if they
are not fused.

Rename the global 'thcode' variable to 'thcodes' to avoid shadowing the
symbol in functions that take it as an argument.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200610003300.884258-1-niklas.soderlund+renesas@ragnatech.se