baseband/fpga_lte_fec: fix crash with debug

baseband/fpga_lte_fec: fix crash with debug

When RTE_LIBRTE_BBDEV_DEBUG is enabled, rte_device's driver
pointer is dereferenced twice in fpga_lte_fec's probe callback.
It causes a segmentation fault because this pointer is only
assigned after probe callback call.

This patch makes use of rte_pci_driver pointer instead

Fixes: efd453698c49 ("baseband/fpga_lte_fec: add driver for FEC on FPGA")
Cc: stable@dpdk.org
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Nicolas Chautru <nicolas.chautru@intel.com>