iio: Fix sysfs attribute verification failing

sysfs usually appends newlines at the end of attributes to make them
easier to consume, but the test suite can't test for that.

** (iio-sensor-proxy:4882): WARNING **: 14:14:46.792: Possible failure in string write of 'accel_3d-dev0
' Should be 'accel_3d-dev0' written to /sys/devices/platform/AMDI0010:02/i2c-2/i2c-BMA250E:00/0018:6243:0001.0002/HID-SENSOR-200073.2.auto/iio:device0/trigger/current_trigger

Closes: #347

Fixes: ac053f8a12

src/iio-buffer-utils.c

@@ -416,7 +416,7 @@ _write_sysfs_string (const char *filename,
 		return 0;
 	g_clear_pointer (&sysfsfp, fclose);
 	if (!g_file_get_contents (temp, &contents, NULL, NULL) ||
-	    g_strcmp0 (contents, val) != 0) {
+	    g_strcmp0 (g_strchomp (contents), val) != 0) {
 		g_warning ("Possible failure in string write of '%s' Should be '%s' written to %s\n",
 			   contents ?: "(null)", val, temp);
 		return -1;