drm/amdgpu: fix build on aarch64.

Same fix went in previously for some other files.
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/amd/powerplay/hwmgr/polaris10_thermal.c

@@ -21,6 +21,7 @@
  *
  */
 
+#include <asm/div64.h>
 #include "polaris10_thermal.h"
 #include "polaris10_hwmgr.h"
 #include "polaris10_smumgr.h"