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

'drm/drm_hdcp.h' included in 'amdgpu_dm.c' is duplicated.
It is also included in the 79th line.
Signed-off-by: Zhang Yunkai <zhang.yunkai@zte.com.cn>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -45,7 +45,6 @@
 #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"