ACPI: thinkpad-acpi: minor hotkey_radio_sw fixes

Fixes some minor points in the radio switch code and docs.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/misc/thinkpad_acpi.c b/drivers/misc/thinkpad_acpi.c
index 3548350..c119cf2 100644
--- a/drivers/misc/thinkpad_acpi.c
+++ b/drivers/misc/thinkpad_acpi.c
@@ -1161,15 +1161,15 @@
 {
 	int wlsw;
 
-	mutex_lock(&tpacpi_inputdev_send_mutex);
-
 	if (tp_features.hotkey_wlsw && !hotkey_get_wlsw(&wlsw)) {
+		mutex_lock(&tpacpi_inputdev_send_mutex);
+
 		input_report_switch(tpacpi_inputdev,
 				    SW_RADIO, !!wlsw);
 		input_sync(tpacpi_inputdev);
-	}
 
-	mutex_unlock(&tpacpi_inputdev_send_mutex);
+		mutex_unlock(&tpacpi_inputdev_send_mutex);
+	}
 }
 
 static void tpacpi_input_send_tabletsw(unsigned int state)