thermal: qcom: tsens-8916: mark PM functions __maybe_unused

thermal: qcom: tsens-8916: mark PM functions __maybe_unused

The newly added tsens-8916 driver produces warnings when CONFIG_PM
is disabled:

drivers/thermal/qcom/tsens.c:53:12: error: 'tsens_resume' defined but not used [-Werror=unused-function]
 static int tsens_resume(struct device *dev)
            ^~~~~~~~~~~~
drivers/thermal/qcom/tsens.c:43:12: error: 'tsens_suspend' defined but not used [-Werror=unused-function]
 static int tsens_suspend(struct device *dev)
            ^~~~~~~~~~~~~

This marks both functions __maybe_unused to let the compiler
know that they might be used in other configurations, without
adding ugly #ifdef logic.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Rajendra Nayak <rnayak@codeaurora.org>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>