thermal: rcar_gen3: Reuse logic to read fuses on Gen3 and Gen4

thermal: rcar_gen3: Reuse logic to read fuses on Gen3 and Gen4

The hardware calibration is fused on some, but not all, Gen3 and Gen4
boards. The calibrations values are the same on both generations but
located at different register offsets.

Instead of having duplicated logic to read the and store the values
create structure to hold the register parameters and have a common
function do the reading.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20250305174631.4119374-3-niklas.soderlund+renesas@ragnatech.se
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>