drm/i915: Remove TC PHY disconnect workaround

After the previous patch the workaround for a TC PHY hang issue is not
required any more, remove it.

Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230323142035.1432621-29-imre.deak@intel.com