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

[ Upstream commit 319aca883bfa1b85ee08411541b51b9a934ac858 ]

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.com
Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>