neighbour.h: fix comment

Signed-off-by: NLi Zhong <zhong@linux.vnet.ibm.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

include/uapi/linux/neighbour.h

@@ -58,7 +58,7 @@ enum {
 
 /* NUD_NOARP & NUD_PERMANENT are pseudostates, they never change
    and make no address resolution or NUD.
-   NUD_PERMANENT is also cannot be deleted by garbage collectors.
+   NUD_PERMANENT also cannot be deleted by garbage collectors.
  */
 
 struct nda_cacheinfo {