drm/panel-lg-lg4573: Fix dotclock

drm/panel-lg-lg4573: Fix dotclock

The currently listed dotclock disagrees with the currently
listed vrefresh rate. Change the dotclock to match the vrefresh.

Someone tell me which (if either) of the dotclock or vreresh is
correct?

Cc: Heiko Schocher <hs@denx.de>
Cc: Thierry Reding <treding@nvidia.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200302203452.17977-7-ville.syrjala@linux.intel.com
Reviewed-by: Heiko Schocher <hs@denx.de>