drm/xe: Use the encoder suspend helper also used by the i915 driver

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