drm/amdgpu: fix typo of CGTS

Fixes: 9e8590861e9 ('drm/amdgpu: add parse clock gating state')
Reported-by: Tom StDenis <Tom.StDenis@amd.com>
Signed-off-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>