drm/msm/dp: DisplayPort PHY compliance tests fixup

Bandwidth code was being used as test link rate. Fix this by converting
bandwidth code to test link rate

Do not reset voltage and pre-emphasis level during IRQ HPD attention
interrupt. Also fix pre-emphasis parsing during test link status process

Signed-off-by: Tanmay Shah <tanmay@codeaurora.org>
Fixes: 8ede2ecc ("drm/msm/dp: Add DP compliance tests on Snapdragon Chipsets")
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>