drm/i915/vbt: update DP max link rate table

According to Bspec #20124, max link rate table for DP was updated
at BDB version 230. Max link rate can support upto UHBR.

After migrate to BDB v230, the definition for LBR, HBR2 and HBR3
were changed. For backward compatibility. If BDB version was
from 216 to 229. Driver have to follow original rule to configure
DP max link rate value from VBT.

v2: split the mapping table to two for old and new BDB definition.
v3: return link rate instead of assigning it.
v4: remove the useless variable.

Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Cooper Chiou <cooper.chiou@intel.com>
Cc: William Tseng <william.tseng@intel.com>
Signed-off-by: Lee Shawn C <shawn.c.lee@intel.com>
[vsyrjala: Try to retain the comment that VBT version 216 added some of this]
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210218052333.16109-1-shawn.c.lee@intel.com