drm/amd/display: set dram speed for all states

[WHY?]
If higher states have memory speed set to 0 MT/s currently they do not get set
to the highest value which can cause validation failures.

[HOW?]
Set unpopulated higher states to max value.

Signed-off-by: Dillon Varone <dillon.varone@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>