drm/msm/dp: reset the link phy params before link training

Before re-starting link training reset the link phy params namely
the pre-emphasis and voltage swing levels otherwise the next
link training begins at the previously cached levels which can result
in link training failures.

Fixes: 8ede2ecc ("drm/msm/dp: Add DP compliance tests on Snapdragon Chipsets")
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Tested-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> # SM8350-HDK
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Patchwork: https://patchwork.freedesktop.org/patch/605946/
Link: https://lore.kernel.org/r/20240725220450.131245-1-quic_abhinavk@quicinc.comSigned-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>

drivers/gpu/drm/msm/dp/dp_ctrl.c

@@ -1286,6 +1286,8 @@ static int dp_ctrl_link_train(struct dp_ctrl_private *ctrl,
 	link_info.rate = ctrl->link->link_params.rate;
 	link_info.capabilities = DP_LINK_CAP_ENHANCED_FRAMING;
 
+	dp_link_reset_phy_params_vx_px(ctrl->link);
+
 	dp_aux_link_configure(ctrl->aux, &link_info);
 
 	if (drm_dp_max_downspread(dpcd))