drm/i915/cx0: Enable/disable TX only for owned PHY lanes

Display must not enable or disable transmitters for not-owned PHY lanes.

BSpec: 64539
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230814131331.69516-4-gustavo.sousa@intel.com