drm/i915: Show LTTPR in the TPS debug print

Indicate which LTTPR we're currently attempting to train when
we print which training pattern we're using.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211004170535.4173-3-ville.syrjala@linux.intel.com
Reviewed-by: Imre Deak <imre.deak@intel.com>