nfp: serialize access for hardware reconfiguration

nfp: serialize access for hardware reconfiguration

Some apps calling some functions from different threads at the
same time could lead to reconfig problems. Reconfig mechanism is
based on a hardware queue where incrementing a counter signals the
firmware to do the reconfig. If there is a second increment before the
first one has been processed the firmware will stop and a device
reset is necessary.

Signed-off-by: Alejandro Lucero <alejandro.lucero@netronome.com>