thermal/core: Use the thermal zone 'devdata' accessor in thermal located drivers

The thermal zone device structure is exposed to the different drivers
and obviously they access the internals while that should be
restricted to the core thermal code.

In order to self-encapsulate the thermal core code, we need to prevent
the drivers accessing directly the thermal zone structure and provide
accessor functions to deal with.

Use the devdata accessor introduced in the previous patch.

No functional changes intended.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se> #R-Car
Acked-by: Mark Brown <broonie@kernel.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com> #MediaTek auxadc and lvts
Reviewed-by: Balsam CHIHI <bchihi@baylibre.com> #Mediatek lvts
Reviewed-by: Adam Ward <DLG-Adam.Ward.opensource@dm.renesas.com> #da9062
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>  #spread
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com> #sun8i_thermal
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com> #Broadcom
Reviewed-by: Dhruva Gole <d-gole@ti.com> # K3 bandgap
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Heiko Stuebner <heiko@sntech.de> #rockchip
Reviewed-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com> #uniphier
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>