aes: remove a dead return statement

bits is checked to be 128, 192 or 256 at the beginning of the function.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

util/aes.c

@@ -1161,7 +1161,7 @@ int AES_set_encrypt_key(const unsigned char *userKey, const int bits,
 			rk += 8;
         	}
 	}
-	return 0;
+        abort();
 }
 
 /**