[PATCH] iio: st_magn: always define ST_MAGN_TRIGGER_SET_STATE

[Arnd Bergmann <arnd@arndb.de>]

When CONFIG_IIO_TRIGGER is enabled but CONFIG_IIO_BUFFER is
not, we get a build error in the st_magn driver:

drivers/iio/magnetometer/st_magn_core.c:573:23: error: 'ST_MAGN_TRIGGER_SET_STATE' undeclared here (not in a function)
  .set_trigger_state = ST_MAGN_TRIGGER_SET_STATE,
                       ^~~~~~~~~~~~~~~~~~~~~~~~~

Apparently, this ST_MAGN_TRIGGER_SET_STATE macro was meant to
be set to NULL when the definition is not available because
st_magn_buffer.c is not compiled, but the alternative definition
was not included in the original patch. This adds it.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 74f5683f35fe ("iio: st_magn: Add irq trigger handling")
---
 drivers/iio/magnetometer/st_magn.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/iio/magnetometer/st_magn.h b/drivers/iio/magnetometer/st_magn.h
index 06a4d9c35581..9daca4681922 100644
--- a/drivers/iio/magnetometer/st_magn.h
+++ b/drivers/iio/magnetometer/st_magn.h
@@ -44,6 +44,7 @@ static inline int st_magn_allocate_ring(struct iio_dev *indio_dev)
 static inline void st_magn_deallocate_ring(struct iio_dev *indio_dev)
 {
 }
+#define ST_MAGN_TRIGGER_SET_STATE NULL
 #endif /* CONFIG_IIO_BUFFER */
 
 #endif /* ST_MAGN_H */
-- 
2.7.0