neighbour: remove stray semicolon

Currently the stray semicolon means that the final term in the addition
is being missed.  Fix this by removing it. Cleans up clang warning:

net/core/neighbour.c:2821:9: warning: expression result unused [-Wunused-value]

Fixes: 82cbb5c631 ("neighbour: register rtnl doit handler")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-By: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/neighbour.c

@@ -2811,7 +2811,7 @@ errout:
 static inline size_t pneigh_nlmsg_size(void)
 {
 	return NLMSG_ALIGN(sizeof(struct ndmsg))
-	       + nla_total_size(MAX_ADDR_LEN); /* NDA_DST */
+	       + nla_total_size(MAX_ADDR_LEN) /* NDA_DST */
 	       + nla_total_size(1); /* NDA_PROTOCOL */
 }