drm/amd/display: enable seamless boot for DCN301

[Why]
DCN301 is capable of running seamless boot
if keep_stolen_vga_memory is not set.

[How]
Add a helper to check whether an ASIC can support
seamless boot and set it based on base driver flags.

Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Zhan Liu <Zhan.Liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>