tools: kmod: add list command

It's the same of lsmod since there's not much to change on its format.
diff --git a/tools/kmod.c b/tools/kmod.c
index 1d48b3f..b6b589a 100644
--- a/tools/kmod.c
+++ b/tools/kmod.c
@@ -36,6 +36,7 @@
 
 static const struct kmod_cmd *kmod_cmds[] = {
 	&kmod_cmd_help,
+	&kmod_cmd_list,
 };
 
 static const struct kmod_cmd *kmod_compat_cmds[] = {