drm/cirrus: fix include notation and remove -Iinclude/drm flag

Include <drm/*.h> instead of relative path from include/drm, then
remove the -Iinclude/drm compiler flag.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1493009447-31524-8-git-send-email-yamada.masahiro@socionext.com

drivers/gpu/drm/cirrus/Makefile

-ccflags-y := -Iinclude/drm
 cirrus-y  := cirrus_main.o cirrus_mode.o \
 	cirrus_drv.o cirrus_fbdev.o cirrus_ttm.o
 

drivers/gpu/drm/cirrus/cirrus_ttm.c

@@ -26,8 +26,9 @@
  * Authors: Dave Airlie <airlied@redhat.com>
  */
 #include <drm/drmP.h>
+#include <drm/ttm/ttm_page_alloc.h>
+
 #include "cirrus_drv.h"
-#include <ttm/ttm_page_alloc.h>
 
 static inline struct cirrus_device *
 cirrus_bdev(struct ttm_bo_device *bd)