drm/i915/bxt: don't use unsupported port detection

The port detection register flags in SFUSE_STRAP and DDI_BUF_CTL_A are
not defined for BXT, so don't use them.

Suggested by Satheesh.

v2:
- DDI_BUF_CTL_A bit 0 is not useful on BXT. Making changes to use this
  bit when simulator or BXT is not applicable. Code re-arranged as per
  Damien's suggestion.

v3:
- clarify commit message, add code comment (imre)

Signed-off-by: Vandana Kannan <vandana.kannan@intel.com> (v2)
Cc: M, Satheeshakrishna <satheeshakrishna.m@intel.com>
Cc: Lespiau, Damien <damien.lespiau@intel.com>
Cc: Shankar, Uma <uma.shankar@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -13011,7 +13011,16 @@ static void intel_setup_outputs(struct drm_device *dev)
 	if (intel_crt_present(dev))
 		intel_crt_init(dev);
 
-	if (HAS_DDI(dev)) {
+	if (IS_BROXTON(dev)) {
+		/*
+		 * FIXME: Broxton doesn't support port detection via the
+		 * DDI_BUF_CTL_A or SFUSE_STRAP registers, find another way to
+		 * detect the ports.
+		 */
+		intel_ddi_init(dev, PORT_A);
+		intel_ddi_init(dev, PORT_B);
+		intel_ddi_init(dev, PORT_C);
+	} else if (HAS_DDI(dev)) {
 		int found;
 
 		/*