kconfig: move ARRAY_SIZE to a header

To use ARRAY_SIZE from other files, move it to its own header,
just like include/linux/array_size.h.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/kconfig/preprocess.c

@@ -9,13 +9,12 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include "array_size.h"
 #include "internal.h"
 #include "list.h"
 #include "lkc.h"
 #include "preprocess.h"
 
-#define ARRAY_SIZE(arr)		(sizeof(arr) / sizeof((arr)[0]))
-
 static char *expand_string_with_args(const char *in, int argc, char *argv[]);
 static char *expand_string(const char *in);