drm/amd/display: Add Bounding Box State for Low DF PState but High Voltage State

[WHY]
DF PState and Voltage State are coupled such that one cannot be
raised without raising the other. This uses more power than
is necessary in high bandwidth scenarios.

[HOW]
Add logic to create a new bounding box state that allows for
DF PState to be low while Voltage State is high. Watermarks
vlevel calculation logic was also udpated to assume
state 1 contains the new optimized state.

Signed-off-by: Sung Lee <sung.lee@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>