drm/i915: Remove a somewhat silly debug print from watermark code

This debug print just adds overhead to the watermark merging process,
and doesn't really give enough information to be useful. Just kill
and let's add something much better a bit later.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>