drm/i915/display/ehl: Add HBR2 and HBR3 voltage swing table

EHL only differs from ICL on the voltage swing table for HBR2 and
HBR3.

BSpec: 21257
Cc: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200205205647.64902-1-jose.souza@intel.com