tools:iio: save errno first

The man-page of errno states, that errno should be saved before doing any
library call, as that call may have changed the value of errno. So, when
encountering any error, save errno first.
This patch affects generic_buffer.c, iio_event_monitor.c and iio_utils.c.

Signed-off-by: Hartmut Knaack <knaack.h@gmx.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/tools/iio/iio_event_monitor.c b/tools/iio/iio_event_monitor.c
index 427c271..f6fdab4 100644
--- a/tools/iio/iio_event_monitor.c
+++ b/tools/iio/iio_event_monitor.c
@@ -269,8 +269,8 @@
 
 	fd = open(chrdev_name, 0);
 	if (fd == -1) {
-		fprintf(stdout, "Failed to open %s\n", chrdev_name);
 		ret = -errno;
+		fprintf(stdout, "Failed to open %s\n", chrdev_name);
 		goto error_free_chrdev_name;
 	}
 
@@ -279,8 +279,8 @@
 	close(fd);
 
 	if (ret == -1 || event_fd == -1) {
-		fprintf(stdout, "Failed to retrieve event fd\n");
 		ret = -errno;
+		fprintf(stdout, "Failed to retrieve event fd\n");
 		goto error_free_chrdev_name;
 	}
 
@@ -291,8 +291,8 @@
 				printf("nothing available\n");
 				continue;
 			} else {
-				perror("Failed to read event from device");
 				ret = -errno;
+				perror("Failed to read event from device");
 				break;
 			}
 		}