drm/amd/display: Fix for variable may be used uninitialized error

[Why]
Build failure due to ‘status’ may be used uninitialized

[How]
Initialize status to LINK_TRAINING_SUCCESS

Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Jasdeep Dhillon <jdhillon@amd.com>
Signed-off-by: Eric Bernstein <eric.bernstein@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>