sandbox: Enable wget command

Enable this so that the tests run.

Fix a few warnings in the code so that CI passes.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Yasuharu Shibata <yasuharu.shibata@gmail.com>
diff --git a/cmd/Kconfig b/cmd/Kconfig
index 8af136d..43f78a5 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -2010,6 +2010,7 @@
 config CMD_WGET
 	bool "wget"
 	select PROT_TCP
+	default y if SANDBOX
 	help
 	  wget is a simple command to download kernel, or other files,
 	  from a http server over TCP.