cryptocheck: Free generated IV after each GMAC test.

Reviewed by:	cem
Sponsored by:	Netflix
Differential Revision:	https://reviews.freebsd.org/D28753

tools/tools/crypto/cryptocheck.c

@@ -1141,6 +1141,7 @@ run_gmac_test(const struct alg *alg, size_t size)
 
 out:
 	free(buffer);
+	free(iv);
 	free(key);
 }