plugins/fastboot: increase operation delay for Quectel EG25-G
plugins/fastboot: increase operation delay for Quectel EG25-G

When flashing bigger firmware packages we would still get an timeout
after 10 minutes. Increasing the delay between read/write operations
from 100ms to 250ms solves that.

fwupd/fwupd,fwupd/fwupd,fwupd/fwupd,fwupd/fwupd