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.

- Return 0 at the end of the script

uboot.env was breaking u-boot boot on Raspberry Pi 3 because of this.

Also added download support on the Raspberry Pi 3.
The following feature has appeared. The FAT partition does not
install the last installed kernel, but the first kernel in the
KFLAVOURS list. This was done in order to enable  u-boot to
default load another kernel, for example std-def.

The feature фкь-кзш4 is available for armh now.