drm/amd/display: Fix handling duplicate planes on one stream

[why]
DML2 does not handle the case when we have
a single stream sourcing 2 or more planes
that are duplicates of one another. To properly
handle this scenario, pipe index to plane index
mapping is used to decide which plane is being
processed and programmed.

[how]
Create static array of pipe index to plane index map.
Populate the array properly and use in appropriate places.

Reviewed-by: Xi (Alex) Liu <xi.liu@amd.com>
Acked-by: Hersen Wu <hersenxs.wu@amd.com>
Signed-off-by: Sung Joon Kim <sungkim@amd.com>
Signed-off-by: Hersen Wu <hersenxs.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>