drm/amd/display: add explicit comparator as default optimization check

[why]
memcmp is vulnerable to regression due to dc_clocks structures not being
organized properly (not "current" clock related structures being at the beginning
of the structure) and causes unnecessary setting of the optimize bit

[how]
add a dcn sepcific comparator, implement for dcn2

Signed-off-by: Jun Lei <Jun.Lei@amd.com>
Reviewed-by: Anthony Koo <Anthony.Koo@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>