thermal: zx2967: Appease the kernel-doc deity

Fix up the following warning when compiled with make W=1:

linux.git/drivers/thermal/zx2967_thermal.c:57: warning: Function
parameter or member 'dev' not described in 'zx2967_thermal_priv'

Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/1b4f6fb91e2e713ad5135f0d40dcded65dee9d0e.1574242756.git.amit.kucheria@linaro.org