Remove write-only opt and useless optlen variables.

This squashes the warning gebnerated by GCC 6.x. Since
variables that are now removed had come documentation
value, put relevant bits in comment, so they can be
resurrected from there when actually needed.

usr.sbin/efibootmgr/efibootmgr.c

@@ -707,10 +707,8 @@ print_loadopt_str(uint8_t *data, size_t datalen)
 	uint8_t *ep = data + datalen;
 	uint8_t *walker = data;
 	efidp dp, edp;
-	void *opt;
 	char buf[1024];
 	int len;
-	int optlen;
 	int rv;
 	int indent;
 
@@ -734,10 +732,11 @@ print_loadopt_str(uint8_t *data, size_t datalen)
 	if (walker > ep)
 		return;
 	edp = (efidp)walker;
-	// Everything left is the binary option args
-	opt = walker;
-	optlen = ep - walker;
-
+	/*
+	 * Everything left is the binary option args
+	 * opt = walker;
+	 * optlen = ep - walker;
+	 */
 	indent = 1;
 	while (dp < edp) {
 		efidp_format_device_path(buf, sizeof(buf), dp,
@@ -753,8 +752,6 @@ print_loadopt_str(uint8_t *data, size_t datalen)
 		}
 		dp = (efidp)((char *)dp + efidp_size(dp));
 	}
-	if (optlen == 0)
-		return;
 }
 
 static char *