drm/amd/display: Set min dcfclk if pipe count is 0

[WHY]
Clocks don't get recalculated in 0 stream/0 pipe configs,
blocking S0i3 if dcfclk gets high enough

[HOW]
Create DCN31 copy of DCN30 bandwidth validation func which
doesn't entirely skip validation in 0 pipe scenarios

Override dcfclk to vlevel 0/min value during validation if pipe
count is 0

Reviewed-by: Eric Yang <Eric.Yang2@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Michael Strauss <michael.strauss@amd.com>
Tested-by: Daniel Wheeler <Daniel.Wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>