drm/amd/display: fix releasing planes when exiting odm

Releasing planes should not release the 2nd odm pipe right away,
this change leaves us with 2 pipes with null planes and same stream
when planes are released during odm.

Signed-off-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>