drm/i915/bdw: Fix DP_AUX_CH_CTL_TIME_OUT setting

Per BSpec, 400us is "BDW+ Do not use this setting." - not just PORT_A.
Set BDW to 600us unconditionally.

v2:
-Split in to two patches (Rodrigo)

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: James Ausmus <james.ausmus@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171012213037.4245-2-james.ausmus@intel.com