- Revert commit for support multiple kernel in iso image.

This reverts commit 02a5231b.
Upstream mkimage has not yet take patches to support packaging
multiple kernels to ISO image. In order to avoid problems, have
to revert this commit.

- New official maintainer antohami@ (blessed by mike@)
- Added grub config file generator for iso images
  (thanks shaba@)
- Expanded support for USB controllers and SD card readers
- Added support for booting on single-board Raspberry Pi 3 and 4
  in EFI mode (u-boot or edk2)
- Added grub-efi bootloader support for rootfs images
- Merged with branches for Workstation, Education,
  Simply Linux, Server, Server-V distributions
- Added a starterkit build profile with a real-time kernel (live)
- Added riscv64 platform support (thanks arei@)
- rootfs: support headless boot via alterator-setup-vnc (thanks arei@)

This is need to working bluetooth with GUI

If there is no Ethernet connection, RPi4 loading stops for 2 minutes.

On Raspberry Pi 3 B Plus with kernel 5.6.16-rpi-un-alt1 occurs
framebuffer error with dtoverlay=vc4-kms-v3d (antohami@)

Changed audio scheduling from timer-based to
interrupt-driven to prevent unwanted crackle.

This trigger file will delete all lines containing fdtdir after
installing a new kernel version.

- Return 0 at the end of the script