Draft: Switch to downstream drivers for DSI support

Previously we used the patches by M. Tretter, M. Vasut et al. proposed for upstream to support the DSI controller in the i.MX8MM. As these patches won't get merged upstream and as some problems occur that do not exist in the downstream NXP driver or have already been worked around there, we will stay with the downstream drivers for now and wait for a stable upstream solution (and maybe an later kernel release) before we switch.

This MR imports the necessary drivers from the lf-5.10.y branch in linux-imx and slightly adjusts them to use the BLK-CTRL driver instead of the downstream reset drivers. The last two commits adjust the devicetrees for the new driver.

This was briefly tested with the Kontron BL i.MX8MM board and a 7" Jenson Display.