drm/amd: Enable seamless boot by default on newer ASICs

Seamless boot can technically be supported as far back as DCN1
but to avoid regressions on older hardware, enable it for DCN3 and
later.

If users report using the module parameter that it works on older
ASICs as well, this can be adjusted.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>