drm/amd/display: Remove integer scaling code from DC and fix cursor

[Why]
Scaling better handled by upper layers before pipe splitting.

[How]
Remove DC code for integer scaling and force cursor update if
viewport or scaling changes occur to prevent underflow from
invalid cursor position.

Signed-off-by: Aric Cyr <aric.cyr@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Anthony Koo <Anthony.Koo@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>