kallsyms: use `ARRAY_SIZE` instead of hardcoded size

This removes one place where the `500` constant is hardcoded.
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Geert Stappers <stappers@stappers.nl>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Co-developed-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

scripts/kallsyms.c

@@ -206,7 +206,7 @@ static struct sym_entry *read_symbol(FILE *in)
 
 	rc = fscanf(in, "%llx %c %499s\n", &addr, &type, name);
 	if (rc != 3) {
-		if (rc != EOF && fgets(name, 500, in) == NULL)
+		if (rc != EOF && fgets(name, ARRAY_SIZE(name), in) == NULL)
 			fprintf(stderr, "Read error or end of file.\n");
 		return NULL;
 	}