drm/i915: Use standard form terminating condition for lane for loops

Use <4 instead of <=3 as the terminating condition for the
loops over the 4 lanes.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211006204937.30774-4-ville.syrjala@linux.intel.com


Reviewed-by: Jani Nikula <jani.nikula@intel.com>