drm/amd/display: enabling seamless boot sequence for dcn2

drm/amd/display: enabling seamless boot sequence for dcn2

[Why]
Seamless boot (building SW state inheriting BIOS-initialized timing) was
enabled on DCN2, including fixes

[How]
Includes fixes for MPC, DPPCLK, and DIG FE mapping/OTG source select/
Pixel clock.

This is part 2 of 2 for seamless boot NV10

Signed-off-by: Martin Leung <martin.leung@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>