Two BSpec updates changed the recommended values for BDW eDP and DP
DDI buffer translations. Now the signal levels also match the HSW signal
levels, which simplify things a little bit.

It seems some DP sinks don't work properly without voltage level 0 and
pre-emphasis level 3, so this patch may fix some bugs on
panels/monitors that happen on BDW but not on HSW.
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: NDamien Lespiau <damien.lespiau@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>