[Why&How]
Driver defaults to 1-tap subsample mode for 4:2:2.
DCE11.2 added 3-tap. The policy is:
DCE8-DCE11 - change to 2-tap, it's better than 1-tap.
DCE11.2+ - use 3-tap

Note that 4:2:0 was added in DCE11.2 and already uses 3-tap always.
Note 2 is that DCE not covered on Linux, only DCN+
Signed-off-by: Krunoslav Kovac <Krunoslav.Kovac@amd.com>
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>