IIO: Move core headers to include/linux/iio

Step 1 in moving the IIO core out of staging.

Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/staging/iio/ring_sw.c b/drivers/staging/iio/ring_sw.c
index b9945ec..9358c6c 100644
--- a/drivers/staging/iio/ring_sw.c
+++ b/drivers/staging/iio/ring_sw.c
@@ -15,7 +15,7 @@
 #include <linux/sched.h>
 #include <linux/poll.h>
 #include "ring_sw.h"
-#include "trigger.h"
+#include <linux/iio/trigger.h>
 
 /**
  * struct iio_sw_ring_buffer - software ring buffer