Revert "more methods to power down display before boot"
This reverts commit 9562dd36
This removes two calls to functions to disable the fb, though
imx8m_fb_disable
: I didn't found an implementation in the current code.
lcdifv3_power_down();
: This function needs to be called with a point to the related device.
With out it it may work on random memory and may result in a crash of u-boot.