Only toggle GPIO #9 when resetting the slave lpGBT

With the appropriate default lpGBT configuration, this commits avoids
any side effect on the master lpGBT from triggering an exernal slave
lpGBT reset. Side effects included, among others, incorrectly setting
the VFAT reset lines GPIO.

Updated default lpGBT configurations will fully configure the GPIO block
for "the system to just work": I/O direction, drive strength,
pull-up/down resistor, reset lifted,...