thermal: exynos: Use devm_* functions

devm_* functions are used to replace kzalloc, request_mem_region, ioremap
and request_irq functions in probe call. With the usage of devm_* functions
explicit freeing and unmapping is not required.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Sachin Kamat <sachin.kamat@samsung.com>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@linaro.org>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>