The source file was moved to base earlier and also improved upon,
but never compiled in. This patch will:
- Make a module in sys/modules
- Make lindebugfs depend on linuxkpi (for seq_file)
- Check if read/write functions are set before calling, DRM drivers
don't always set both of them.
Reviewed by: hps
Approved by: imp (mentor), hps
MFC after: 1 week