drm/amd/display: Honor pplib stutter mask for all ASICs in DC

[Why]
We were only setting this mask for DCN, but should really use it
universally for all ASICs.

[How]
Move the assignment out of the Raven switch statement for all ASICs
other than Stoney and Carrizo.

v2: Keep stutter always on for Carrizo and Stoney (Alex)

Cc: Rex.Zhu@amd.com
Cc: Feifei.Xu@amd.com
Cc: Kenneth.Feng@amd.com
Cc: Evan.Quan@amd.com
Cc: Bhawanpreet.Lakha@amd.com
Cc: Jordan.Lazare@amd.com
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>