drm/amd/display: Only put primary planes into the mode_info->planes list

drm/amd/display: Only put primary planes into the mode_info->planes list

We want DRM planes to be initialized in the following order:

- primary planes
- overlay planes
- cursor planes

to support existing userspace expectations for plane z-ordering. This
means that we also need to register CRTCs after all planes have been
initialized since overlay planes can be placed on any CRTC.

So the only reason why we have the mode_info->planes list is to
remember the primary planes for use later when we need to register
the CRTC.

Overlay planes have no purpose being in this list. DRM will cleanup
any planes that we've registered for us, so the only planes that need to
be explicitly cleaned up are the ones that have failed to register.

By dropping the explicit free on every plane in the mode_info->planes
list this patch also fixes a double-free in the case where we fail to
initialize only some of the planes.

Cc: Leo Li <sunpeng.li@amd.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>