Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/include/linux/iio/timer/stm32-lptim-trigger.h b/include/linux/iio/timer/stm32-lptim-trigger.h
index 464458d..a34dcf6 100644
--- a/include/linux/iio/timer/stm32-lptim-trigger.h
+++ b/include/linux/iio/timer/stm32-lptim-trigger.h
@@ -1,9 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
 /*
  * Copyright (C) STMicroelectronics 2017
  *
  * Author: Fabrice Gasnier <fabrice.gasnier@st.com>
- *
- * License terms:  GNU General Public License (GPL), version 2
  */
 
 #ifndef _STM32_LPTIM_TRIGGER_H_
diff --git a/include/linux/iio/timer/stm32-timer-trigger.h b/include/linux/iio/timer/stm32-timer-trigger.h
index d68add8..37572e4 100644
--- a/include/linux/iio/timer/stm32-timer-trigger.h
+++ b/include/linux/iio/timer/stm32-timer-trigger.h
@@ -1,9 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
 /*
  * Copyright (C) STMicroelectronics 2016
  *
  * Author: Benjamin Gaignard <benjamin.gaignard@st.com>
- *
- * License terms:  GNU General Public License (GPL), version 2
  */
 
 #ifndef _STM32_TIMER_TRIGGER_H_
@@ -73,6 +72,15 @@
 
 #define TIM17_OC1	"tim17_oc1"
 
+#if IS_REACHABLE(CONFIG_IIO_STM32_TIMER_TRIGGER)
 bool is_stm32_timer_trigger(struct iio_trigger *trig);
-
+#else
+static inline bool is_stm32_timer_trigger(struct iio_trigger *trig)
+{
+#if IS_ENABLED(CONFIG_IIO_STM32_TIMER_TRIGGER)
+	pr_warn_once("stm32-timer-trigger not linked in\n");
+#endif
+	return false;
+}
+#endif
 #endif