drm/amd/display: disable seamless boot for VSC_SDP

[WHY]
VBIOS will not enable VSC_SDP during pre-OS to lead
MISC1[6] wasn't matched with driver.

[HOW]
disabled seamless boot if sink supports VSC_SDP

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