drm/amd/display: Remove duplicate dml init

[Why & How]
DML is initialized again unnecessarily after its done conditionally.
Remove the duplicate initialization

Bug: drm/amd#1403


Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>