drm/amd/display: Use dcn1 Optimal Taps Get

[WHY]
dpp2_get_optimal_number_of_taps is incorrect, and dcn2 should be using
dpp1_get_optimal_number_of_taps instead

Signed-off-by: Wesley Chalmers <Wesley.Chalmers@amd.com>
Reviewed-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>