mfd: intel_soc_pmic: Add CONFIG_PM_SLEEP check for suspend_fn/resume_fn

This patch fix warning message with CONFIG_PM_SLEEP disabled
If CONFIG_PM_SLEEP is not enabled we receive the following warning message:

drivers/mfd/intel_soc_pmic_core.c:118:12:
 warning: 'intel_soc_pmic_suspend' defined but not used
Signed-off-by: NJaewon Kim <jaewon02.kim@samsung.com>
Signed-off-by: NLee Jones <lee.jones@linaro.org>

drivers/mfd/intel_soc_pmic_core.c

@@ -115,6 +115,7 @@ static void intel_soc_pmic_shutdown(struct i2c_client *i2c)
 	return;
 }
 
+#if defined(CONFIG_PM_SLEEP)
 static int intel_soc_pmic_suspend(struct device *dev)
 {
 	struct intel_soc_pmic *pmic = dev_get_drvdata(dev);
@@ -132,6 +133,7 @@ static int intel_soc_pmic_resume(struct device *dev)
 
 	return 0;
 }
+#endif
 
 static SIMPLE_DEV_PM_OPS(intel_soc_pmic_pm_ops, intel_soc_pmic_suspend,
 			 intel_soc_pmic_resume);