Some devices (motorola-dubai) need to access readwrite files found in the
persist partition in `rfs/msm/mpss` to have working modem.
Create a new systemd unit that calls a shell script to copy the files
into the readwrite folder (currently /var/lib/tqftpserv).
The units runs only if and after /dev/disk/by-partlabel/persist is available.
Signed-off-by: Federico Amedeo Izzo <federico@izzo.pro>
