drm/i915: try harder to find WR PLL clock settings

If we don't find the exact refresh rate, go with the next one. This
makes some modes work for me. They won't have the best settings, but
will at least have something. Just returning from this function when
we don't find the perfect settings does not help us at all.

Version 2:
  - Remove duplicate lines on the clock table.
  - Add back debug message with refresh, p, n2 and r2.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>