drm/amd/display: Add missing DET segments programming

The commit 5034b935 ("drm/amd/display: Modify DHCUB waterwark
structures and functions") introduced a code refactor for DCHUB, but
during the merge process into amd-staging-drm-next, the program det
segments were removed. This commit adds the DET segment programming for
DCN35.

Fixes: 5034b935 ("drm/amd/display: Modify DHCUB waterwark structures and functions")
Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 675d9ac9)