thermal: qoriq: Drop unnecessary drvdata cleanup

Driver data of underlying struct device will be set to NULL by Linux's
driver infrastructure. Clearing it here is unnecessary.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Tested-by: Lucas Stach <l.stach@pengutronix.de>
Cc: Chris Healy <cphealy@gmail.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Eduardo Valentin <edubezval@gmail.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Angus Ainslie (Purism) <angus@akkea.ca>
Cc: linux-imx@nxp.com
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20191210164153.10463-8-andrew.smirnov@gmail.com