PC-BSD/trueos 8023339sys/compat/lindebugfs lindebugfs.c, sys/modules Makefile

LinuxKPI: Finalize move of lindebugfs from ports to base.

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
DeltaFile
+12-4sys/compat/lindebugfs/lindebugfs.c
+12-0sys/modules/lindebugfs/Makefile
+1-0sys/modules/Makefile
+25-43 files

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