hwmon: (core) Avoid cyclic dependency between hwmon and thermal_sys

If both hwmon and thermal_sys are built as modules, and
CONFIG_THERMAL_HWMON is enabled, the following cyclic module dependency
is reported.

depmod: ERROR: Found 2 modules in dependency cycles!
depmod: ERROR: Cycle detected: hwmon -> thermal_sys -> hwmon

Fixes: e4bce763adb2 ("hwmon: (core) New hwmon registration API")
Reported-by: Vignesh R <vigneshr@ti.com>
Cc: Keerthy J <j-keerthy@ti.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/hwmon.c

@@ -108,7 +108,13 @@ static DEFINE_IDA(hwmon_ida);
 
 /* Thermal zone handling */
 
-#if IS_REACHABLE(CONFIG_THERMAL) && defined(CONFIG_THERMAL_OF)
+/*
+ * The complex conditional is necessary to avoid a cyclic dependency
+ * between hwmon and thermal_sys modules.
+ */
+#if IS_REACHABLE(CONFIG_THERMAL) && defined(CONFIG_THERMAL_OF) && \
+	(!defined(CONFIG_THERMAL_HWMON) || \
+	 !(defined(MODULE) && IS_MODULE(CONFIG_THERMAL)))
 static int hwmon_thermal_get_temp(void *data, int *temp)
 {
 	struct hwmon_thermal_data *tdata = data;
@@ -153,7 +159,7 @@ static int hwmon_thermal_add_sensor(struct device *dev,
 {
 	return 0;
 }
-#endif /* IS_REACHABLE(CONFIG_THERMAL) && defined(CONFIG_THERMAL_OF) */
+#endif /* IS_REACHABLE(CONFIG_THERMAL) && ... */
 
 /* sysfs attribute management */