drm/amd/display: Fix memleak on input transfer function

Input transfer function creation is now done when the plane is created.
This is done within the following change:

    Author: Anthony Koo <Anthony.Koo@amd.com>
        drm/amd/display: Have DC manage its own allocation of gamma

Therefore, we no longer need to create it when filling in the plane
attributes.

Signed-off-by: Leo (Sunpeng) Li <sunpeng.li@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>