drm/amd/display: Add DC Debug mask to disable features for bringup

[Why]
At bringup we want to be able to disable various power features.

[How]
These features are already exposed as dc_debug_options and exercised
on other OSes. Create a new dc_debug_mask module parameter and expose
relevant bits, in particular
 * DC_DISABLE_PIPE_SPLIT
 * DC_DISABLE_STUTTER
 * DC_DISABLE_DSC
 * DC_DISABLE_CLOCK_GATING

Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu.h

@@ -173,6 +173,7 @@ extern int amdgpu_gpu_recovery;
 extern int amdgpu_emu_mode;
 extern uint amdgpu_smu_memory_pool_size;
 extern uint amdgpu_dc_feature_mask;
+extern uint amdgpu_dc_debug_mask;
 extern uint amdgpu_dm_abm_level;
 extern struct amdgpu_mgpu_info mgpu_info;
 extern int amdgpu_ras_enable;