* meson-s4t7: bump u-boot to khadas-vims-u-boot-2019.01-v1.6-release
* Use khadas default bootargs as much as possible
* Add new hook to allow copying code into kernel
* meson-s4t7: legacy: Switch to 5.15 kernel
* meson-s4t7: add kernel-config for 5.15 kernel
* device tree overlays for 5.15 kernel for vim1s and vim4
* restructure packaging of bsp files for vim1s/vim4
* silence vblank warning on boot
* Remove display workaround as it doesn't work with 5.15 kernel
* Remove 5.4 kernel patches
