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
diff --git a/drivers/gpu/drm/amd/amdgpu/si.c b/drivers/gpu/drm/amd/amdgpu/si.c
index c0b1aab..2431639 100644
--- a/drivers/gpu/drm/amd/amdgpu/si.c
+++ b/drivers/gpu/drm/amd/amdgpu/si.c
@@ -24,7 +24,7 @@
 #include <linux/firmware.h>
 #include <linux/slab.h>
 #include <linux/module.h>
-#include "drmP.h"
+#include <drm/drmP.h>
 #include "amdgpu.h"
 #include "amdgpu_atombios.h"
 #include "amdgpu_ih.h"