drm/panel: s6e8aa0: Use standard MIPI DSI function

Use the newly introduced mipi_dsi_set_maximum_return_packet_size()
function to replace an open-coded version.

Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>

diff --cc drivers/gpu/drm/panel/panel-s6e8aa0.c
Simple merge