Revert "drm/amd/display: remove duplicate include in amdgpu_dm.c"

This reverts commit 51713e4e.

The duplicate from #79 should be removed instead.
Signed-off-by: Anson Jacob <Anson.Jacob@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -45,6 +45,7 @@
 #include "amdgpu_dm.h"
 #ifdef CONFIG_DRM_AMD_DC_HDCP
 #include "amdgpu_dm_hdcp.h"
+#include <drm/drm_hdcp.h>
 #endif
 #include "amdgpu_pm.h"