drm/i915: Don't send idle pattern after DP2.0 link training

Bspec calls us to select pattern 2 after link training for
DP 2.0. Let's do that... by doing nothing because we will
be transmitting pattern 2 at the end of the link training
already.

Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230308212627.7601-2-ville.syrjala@linux.intel.com