thermal: sysfs: remove symbols of emul_temp when config is disabled

Remove the following warning:
In file included from drivers/thermal/thermal_sysfs.c:19:0:
include/linux/device.h:575:26: warning: ‘dev_attr_emul_temp’ defined but not used [-Wunused-variable]
  struct device_attribute dev_attr_##_name = __ATTR(_name, _mode, _show, _store)
                          ^
drivers/thermal/thermal_sysfs.c:395:8: note: in expansion of macro ‘DEVICE_ATTR’

when emul temp is disabled at Kconfig.

Cc: Zhang Rui <rui.zhang@intel.com>
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>

drivers/thermal/thermal_sysfs.c

@@ -292,6 +292,7 @@ available_policies_show(struct device *dev, struct device_attribute *devattr,
 	return thermal_build_list_of_policies(buf);
 }
 
+#if (IS_ENABLED(CONFIG_THERMAL_EMULATION))
 static ssize_t
 emul_temp_store(struct device *dev, struct device_attribute *attr,
 		const char *buf, size_t count)
@@ -316,6 +317,8 @@ emul_temp_store(struct device *dev, struct device_attribute *attr,
 
 	return ret ? ret : count;
 }
+static DEVICE_ATTR(emul_temp, S_IWUSR, NULL, emul_temp_store);
+#endif
 
 static ssize_t
 sustainable_power_show(struct device *dev, struct device_attribute *devattr,
@@ -395,7 +398,6 @@ create_s32_tzp_attr(offset);
  */
 static DEVICE_ATTR(type, 0444, type_show, NULL);
 static DEVICE_ATTR(temp, 0444, temp_show, NULL);
-static DEVICE_ATTR(emul_temp, S_IWUSR, NULL, emul_temp_store);
 static DEVICE_ATTR(policy, S_IRUGO | S_IWUSR, policy_show, policy_store);
 static DEVICE_ATTR(available_policies, S_IRUGO, available_policies_show, NULL);
 static DEVICE_ATTR(sustainable_power, S_IWUSR | S_IRUGO, sustainable_power_show,