drm/i915/dp: return proper DPRX link training result

After DPRX link training, intel_dp_link_train_phy() did not
return the training result properly. If link training failed,
i915 driver would not run into link train fallback function.
And no hotplug uevent would be received by user space application.

Fixes: b30edfd ("drm/i915: Switch to LTTPR non-transparent mode link training")
Cc: Ville Syrjala <[email protected]>
Cc: Imre Deak <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Cooper Chiou <[email protected]>
Cc: William Tseng <[email protected]>
Signed-off-by: Lee Shawn C <[email protected]>
Reviewed-by: Imre Deak <[email protected]>
Signed-off-by: Imre Deak <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
(cherry picked from commit dab1b47)
Signed-off-by: Jani Nikula <[email protected]>

Author: ShawnCLee

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

@@ -848,7 +848,7 @@ intel_dp_link_train_all_phys(struct intel_dp *intel_dp,
 	}
 
 	if (ret)
-		intel_dp_link_train_phy(intel_dp, crtc_state, DP_PHY_DPRX);
+		ret = intel_dp_link_train_phy(intel_dp, crtc_state, DP_PHY_DPRX);
 
 	if (intel_dp->set_idle_link_train)
 		intel_dp->set_idle_link_train(intel_dp, crtc_state);