drm/i915/display: Handle lane polarity for DDI port

Lane Reversal is required for some of the DDI ports. This information
is populated in VBT and driver should read the same and set the
polarity while enabling the port. This patch handles the same.

It helps fix a display blankout issue on DP ports on certain
platforms.

Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210211114209.23866-1-uma.shankar@intel.com