drm/amd/display: removing MODULO change for dcn2

[why]
when resetting pipes from 480p to dual-pipe 8k, modulo reg write for
video optimized rate updated one pipe without changing the other, causing
sync error

[how]
removed code from dcn2

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>