drm/amd/display: Fix unused variable compilation error

Fix:

drivers/gpu/drm/amd/amdgpu/../dal-dev/dc/dce110/dce110_hw_sequencer.c:
In function ‘dce110_blank_stream’:
drivers/gpu/drm/amd/amdgpu/../dal-dev/dc/dce110/dce110_hw_sequencer.c:1008:31:
error: unused variable ‘params’ [-Werror=unused-variable]
  struct encoder_unblank_param params = { { 0 } };

Signed-off-by: Leo (Sunpeng) Li <sunpeng.li@amd.com>
Reviewed-by: Wesley Chalmers <Wesley.Chalmers@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>