drm/amd/display: remove output_tf_change flag

drm/amd/display: remove output_tf_change flag

Remove this flag as the driver stopped managing it individually since
commit a4056c2a6344 ("drm/amd/display: use HW hdr mult for brightness
boost"). After some back and forth it was reintroduced as a condition to
`set_output_transfer_func()` in [1]. Without direct management, this
flag only changes value when all surface update flags are set true on
UPDATE_TYPE_FULL with no output TF status meaning.

Fixes: bb622e0c0044 ("drm/amd/display: program output tf when required") [1]
Signed-off-by: Melissa Wen <mwen@igalia.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>