drm/msm/dp: remove max_pclk_khz field from dp_panel/dp_display

Since the last commit, the max_pclk_khz became constant, it's set to
DP_MAX_PIXEL_CLK_KHZ and never changed afterwards. Remove it completely
and use DP_MAX_PIXEL_CLK_KHZ directly.

Reviewed-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/480139/
Link: https://lore.kernel.org/r/20220330223008.649274-4-dmitry.baryshkov@linaro.org
[DB: applied a fix to follow connector->bridge conversion]
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>