lib: remove uncessary #includes from headers

Only include what the header itself needs. The big fish here is
intel-gpu-tools.h. More will follow.

One ugly thing removed here is the duplicated GEN6_TD_CTL #define, one
of which was broken.

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

lib/igt_debugfs.h

@@ -27,9 +27,8 @@
 
 #include <stdbool.h>
 #include <stdint.h>
-#include <stdio.h>
 
-#include "igt_display.h"
+enum pipe;
 
 int igt_debugfs_open(const char *filename, int mode);
 FILE *igt_debugfs_fopen(const char *filename,