setkey: Use nitems(foo) instead of sizeof(foo)/sizeof(foo[0])

Pull Request: https://github.com/freebsd/freebsd-src/pull/888
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>

sbin/setkey/setkey.c

@@ -502,7 +502,7 @@ static const char *ipproto[] = {
 };
 
 #define STR_OR_ID(x, tab) \
-	(((x) < sizeof(tab)/sizeof(tab[0]) && tab[(x)])	? tab[(x)] : numstr(x))
+	(((x) < nitems(tab) && tab[(x)]) ? tab[(x)] : numstr(x))
 
 const char *
 numstr(int x)