Use the suspend encoders helper which is also used by the i915 driver.
This fixes an issue in the xe driver where the encoder
suspend_complete() hook is not called and was an overlook when this hook
was added in commit b61fad5f ("drm/i915/tc: Call TypeC port
flush_work/cleanup without modeset locks held") for i915, but not added
to the xe driver (which was still in a separate source tree at the above
point).

v2: Fix checkpatch warn in commit log. (Rodrigo)
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240618125255.4080303-3-imre.deak@intel.com