Programming cards in parallel does not work quite well. At best the
GN412x chip reports errors on all plugged cards. In other cases it
freezes the PC.

With this patch I am going to serialize the FCL access. Like this
cards will be programmed one after the other.

I do not know the origin of the bug, but it must be in the GN412x chip.
Signed-off-by: Federico Vaga <federico.vaga@cern.ch>