tools: add static-nodes tool

This tool reads modules.devname from the current kernel directory and outputs
the information. By default in a human-readable format, and optionally in
machine-readable formats.

For now only the tmpfiles.d(5) format is supported, but more could easily be
added in the future if there is a need.

This means nothing but kmod needs to reads the private files under
/lib/modules/. In particular systemd-udevd can stop reading modules.devname.

Tools that used to read /lib/modules/`uname -r`/modules.devname directly, can
now move to reading 'kmod static-nodes devname'.
diff --git a/tools/kmod.c b/tools/kmod.c
index ebb8875..347bb7d 100644
--- a/tools/kmod.c
+++ b/tools/kmod.c
@@ -37,6 +37,7 @@
 static const struct kmod_cmd *kmod_cmds[] = {
 	&kmod_cmd_help,
 	&kmod_cmd_list,
+	&kmod_cmd_static_nodes,
 };
 
 static const struct kmod_cmd *kmod_compat_cmds[] = {