net: fix a comment typo

Fix a comment typo.
Signed-off-by: NZhang Shengju <zhangshengju@cmss.chinamobile.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/uapi/linux/if.h

@@ -37,7 +37,7 @@
  * are shared for all types of net_devices. The sysfs entries are available
  * via /sys/class/net/<dev>/flags. Flags which can be toggled through sysfs
  * are annotated below, note that only a few flags can be toggled and some
- * other flags are always always preserved from the original net_device flags
+ * other flags are always preserved from the original net_device flags
  * even if you try to set them via sysfs. Flags which are always preserved
  * are kept under the flag grouping @IFF_VOLATILE. Flags which are volatile
  * are annotated below as such.