thermal: exynos: Fix potential NULL pointer dereference

NULL pointer was being dereferenced in its own error message.
Changed it to the correct device pointer.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Eduardo Valentin <eduardo.valentin@ti.com>

diff --cc drivers/thermal/samsung/exynos_thermal_common.c
Simple merge