drm/i915: Remove ILK-A eDP PLL workaround notes

We don't care about ILK-A and the old w/a notes may just confuse
people, so get rid of them.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1446146763-31821-12-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>