Add buildroot utils/check-package check to the pr-checks.yml workflow.
It checks for common errors/mistakes when creating own buildroot
packages. Also fixed all warnings this utility output for our existing packages.
* add eq3_char_loop package (eQ-3 char loopback kernel module)
* add generic_raw_uart package (low-latency raw UART kernel driver)
* add rpi-rf-mod package
* add device tree overlay support for RPI-RF-MOD/HM-MOD-RPI-PCB on Raspberry Pi
* enable GPIOLIB and GPIO_SYSFS required for RPI-RF-MOD/HM-MOD-RPI-PCB support.
* add basic RPI-RF-MOD/HM-MOD-RPI-PCB support for ASUS Tinker Board
* add device tree overlay support for ASUS Tinker Board and add
haos-config.txt loading support to U-Boot boot script
