drm: move intel-gtt.h under include/drm/intel

Clean up the top level include/drm directory by grouping all the Intel
specific files under a common subdirectory.

Cc: Daniel Vetter <[e-mail]>
Cc: Dave Airlie <[e-mail]>
Cc: Lucas De Marchi <[e-mail]>
Reviewed-by: Andi Shyti <[e-mail]>
Acked-by: Lucas De Marchi <[e-mail]>
Acked-by: Rodrigo Vivi <[e-mail]>
Signed-off-by: Jani Nikula <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/ae2[e-mail]

drivers/char/agp/intel-agp.c

···
 #include <asm/smp.h>
 #include "agp.h"
 #include "intel-agp.h"
-#include <drm/intel-gtt.h>
+#include <drm/intel/intel-gtt.h>
 
 static int intel_fetch_size(void)
 {

drivers/char/agp/intel-gtt.c

···
 #include <asm/smp.h>
 #include "agp.h"
 #include "intel-agp.h"
-#include <drm/intel-gtt.h>
+#include <drm/intel/intel-gtt.h>
 #include <asm/set_memory.h>
 
 /*

drivers/gpu/drm/i915/gt/intel_ggtt.c

···
 
 #include <drm/drm_managed.h>
 #include <drm/i915_drm.h>
-#include <drm/intel-gtt.h>
+#include <drm/intel/intel-gtt.h>
 
 #include "display/intel_display.h"
 #include "gem/i915_gem_lmem.h"

drivers/gpu/drm/i915/gt/intel_ggtt_gmch.c

···
 
 #include "intel_ggtt_gmch.h"
 
-#include <drm/intel-gtt.h>
+#include <drm/intel/intel-gtt.h>
 
 #include <linux/agp_backend.h>
 

drivers/gpu/drm/i915/gt/intel_gt.c

···
  */
 
 #include <drm/drm_managed.h>
-#include <drm/intel-gtt.h>
+#include <drm/intel/intel-gtt.h>
 
 #include "gem/i915_gem_internal.h"
 #include "gem/i915_gem_lmem.h"