Since commit 8208181fe536 ("clk: imx: composite-8m:
Add imx8m_divider_determine_rate") the lcdif controller has
had the ability to set the disp_pixel_clk rate which propagates
up the tree and sets the video_pll rate automatically.
As such, there is no need to define it in the board file.
Signed-off-by: Adam Ford <aford173@gmail.com> Signed-off-by: Shawn Guo <shawnguo@kernel.org>