drm/amdgpu/vcn2.5: fix warning

Fix warning during switching to dpg pause mode for
VCN firmware Version ENC: 1.1 DEC: 1 VEP: 0 Revision: 16

Signed-off-by: James Zhu <James.Zhu@amd.com>
Acked-by: Leo Liu <leo.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>