[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>