Brovi Sticks won't work on first-boot

[jonashoechst]

The brovi_startup script will power-toggle the usb ports a modem is connected to on boot, to make the sticks work on RPi 4 devices. However, the timing on first-boot seems to be off, which make the current implementation not work under those conditions.

[jonashoechst]

first-boot is working differently compared to older raspbian versions, there is no reboot after initial partition resizing. Therefore the initial boot having different timing, which is not handled correctly in the current version.