drm/i915: Remove WA for swapped HPD pins in broxton A stepping

Remove workaround for swapped HPD pins in broxton A stepping, which is
pre-production hardware.

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170203140316.20792-1-ander.conselvan.de.oliveira@intel.com