drm/amd/display: Add V_TOTAL_REGS to dcn10

DCN10 OPTC is used by other DCNs, and in some cases it might be useful
to have V_TOTAL_REGS available. This commit add V_TOTAL_REGS as part of
the TG field.

Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>