drm/xe/dp: Enable DP tunneling

Enable the DP tunneling functionality in the xe driver.

v2: Keep using IS_ENABLED() for kconfig options. (Jani)

Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250114122857.1050090-1-imre.deak@intel.com