drm/amd: 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>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1493009447-31524-4-git-send-email-yamada.masahiro@socionext.com

drivers/gpu/drm/amd/amdkfd/Makefile

@@ -2,7 +2,7 @@
 # Makefile for Heterogenous System Architecture support for AMD GPU devices
 #
 
-ccflags-y := -Iinclude/drm -Idrivers/gpu/drm/amd/include/  \
+ccflags-y := -Idrivers/gpu/drm/amd/include/  \
 		-Idrivers/gpu/drm/amd/include/asic_reg
 
 amdkfd-y	:= kfd_module.o kfd_device.o kfd_chardev.o kfd_topology.o \