drm/amd/display: Temporarily disable stutter on MPO transition

[Why]
Underflow sometimes occurs during transition into MPO with stutter
enabled.

[How]
When transitioning into MPO, disable stutter. Re-enable stutter within
one frame.

Signed-off-by: George Shen <george.shen@amd.com>
Signed-off-by: Tony Cheng <tony.cheng@amd.com>
Reviewed-by: Eric Yang <eric.yang2@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>