lib: move prefault helpers to igt_debugfs.c

This way all debugfs library code is in one place, ready for some api
documentation care.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

tests/gem_exec_faulting_reloc.c

@@ -41,6 +41,7 @@
 #include "drmtest.h"
 #include "intel_chipset.h"
 #include "intel_gpu_tools.h"
+#include "igt_debugfs.h"
 
 /* Testcase: Submit patches with relocations in memory that will fault
  *

tests/gem_mmap_gtt.c

@@ -38,6 +38,7 @@
 #include "drm.h"
 #include "i915_drm.h"
 #include "drmtest.h"
+#include "igt_debugfs.h"
 
 static int OBJECT_SIZE = 16*1024*1024;