drm/i915/dp: Do not switch aux to TBT mode for non-TC ports

Non-TC ports always have tc_mode == TC_PORT_TBT_ALT so it was
switching aux to TBT mode for all combo-phy ports, happily this did
not caused any issue but is better follow BSpec.
Also this is reserved bit before ICL.

Cc: Imre Deak <imre.deak@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Fixes: e9b7e142 ("drm/i915: Sanitize the terminology used for TypeC port modes")
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191029011014.286885-1-jose.souza@intel.com

drivers/gpu/drm/i915/display/intel_dp.c

@@ -1293,6 +1293,9 @@ static u32 skl_get_aux_send_ctl(struct intel_dp *intel_dp,
 				u32 unused)
 {
 	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
+	struct drm_i915_private *i915 =
+			to_i915(intel_dig_port->base.base.dev);
+	enum phy phy = intel_port_to_phy(i915, intel_dig_port->base.port);
 	u32 ret;
 
 	ret = DP_AUX_CH_CTL_SEND_BUSY |
@@ -1305,7 +1308,8 @@ static u32 skl_get_aux_send_ctl(struct intel_dp *intel_dp,
 	      DP_AUX_CH_CTL_FW_SYNC_PULSE_SKL(32) |
 	      DP_AUX_CH_CTL_SYNC_PULSE_SKL(32);
 
-	if (intel_dig_port->tc_mode == TC_PORT_TBT_ALT)
+	if (intel_phy_is_tc(i915, phy) &&
+	    intel_dig_port->tc_mode == TC_PORT_TBT_ALT)
 		ret |= DP_AUX_CH_CTL_TBT_IO;
 
 	return ret;