drm/i915/dg1: Update comp master/slave relationships for PHYs

As with RKL, DG1's PHY C acts as a comp master for PHY D.

Bspec: 49291
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201007002210.3678024-7-lucas.demarchi@intel.com