drivers: thermal: make usage of CONFIG_THERMAL_HWMON optional

When registering a new thermal_device, the thermal framework
will always add a hwmon sysfs interface.

This patch adds a flag to make this behavior optional. Now
when registering a new thermal device, the caller can
optionally inform if hwmon interface is desirable. This can
be done by means of passing a thermal_zone_params.no_hwmon == true.

In order to keep same behavior as of today, all current
calls will by default create the hwmon interface.

Cc: David Woodhouse <dwmw2@infradead.org>
Cc: linux-acpi@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Cc: Zhang Rui <rui.zhang@intel.com>
Suggested-by: Wei Ni <wni@nvidia.com>
Signed-off-by: Eduardo Valentin <eduardo.valentin@ti.com>
diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 247528b..51648bf 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -1462,9 +1462,11 @@
 
 	mutex_unlock(&thermal_governor_lock);
 
-	result = thermal_add_hwmon_sysfs(tz);
-	if (result)
-		goto unregister;
+	if (!tz->tzp || !tz->tzp->no_hwmon) {
+		result = thermal_add_hwmon_sysfs(tz);
+		if (result)
+			goto unregister;
+	}
 
 	mutex_lock(&thermal_list_lock);
 	list_add_tail(&tz->node, &thermal_tz_list);