mmc: dw_mmc-rockchip: Add missing private data for very old controllers

In the Linux kernel, the following vulnerability has been resolved: mmc: dw_mmc-rockchip: Add missing private data for very old controllers The really old controllers (rk2928, rk3066, rk3188) do not support UHS speeds at all, and thus never handled phase data. For that reason it never had a parse_dt callback and no driver private data at all. Commit ff6f0286c896 ("mmc: dw_mmc-rockchip: Add memory clock auto-gating support") makes the private data sort of mandatory, because the init function checks whether phases are configured internally or through the clock controller. This results in the old SoCs then experiencing NULL-pointer dereferences when they try to access that private-data struct. While we could have if (priv) conditionals in all places, it's way less cluttery to just give the old types their private-data struct.