drm/amd/display: support plane clip with zero recout size

[why]
If plane clip is outside current pipe's ODM slice rect, our logic will
fail validation because we assume that when a pipe is acquired
to support a plane clip, it must blend some portion of the plane
on the screen. This assumption needs to be changed.
When a pipe is acquired to render the plane, we are now allowing
it to support a case where it can take minimum viewport and draw
with zero recout size when the plane clip is outside current ODM
slice rect. The reason is that we want to allocate and get the pipe
pre-programmed so it is ready to be rendered when user moves
the plane over to the current ODM slice with a fast update.
Whereas with the existing solution when user moves the plane
over, we will need to allocate a pipe as needed and power it up
and program it through a full update. This not only impacts the
user experience with unnecessary delay of a frame but also
doesn't generate any benefit to the user because DML doesn't
support it. DML will invalidate based on worst case scenario and
it doesn't depend on the plane location. So having our
programming sequence support such dynamic pipe allocation is
not meaningful anyway.

[how]
In build scaler params allow recout to be zero size and if viewport
is smaller than minimum, set minimum viewport size.

Reviewed-by: Jun Lei <jun.lei@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>