sign-file: Fix warning about BIO_reset() return value

Fix the following warning:

	scripts/sign-file.c: In function ‘main’:
	scripts/sign-file.c:188: warning: value computed is not used

whereby the result of BIO_ctrl() is cast inside of BIO_reset() to an
integer of a different size - which we're not checking but probably should.

Reported-by: James Morris <jmorris@namei.org>
Signed-off-by: David Howells <dhowells@redhat.com>

scripts/sign-file.c

@@ -185,7 +185,7 @@ int main(int argc, char **argv)
 	ERR(!b, "%s", x509_name);
 	x509 = d2i_X509_bio(b, NULL); /* Binary encoded X.509 */
 	if (!x509) {
-		BIO_reset(b);
+		ERR(BIO_reset(b) != 1, "%s", x509_name);
 		x509 = PEM_read_bio_X509(b, NULL, NULL, NULL); /* PEM encoded X.509 */
 		if (x509)
 			drain_openssl_errors();