bus/ifpga: fix error check in unplug
bus/ifpga: fix error check in unplug

The control variable should be afu_dev not dev.

Coverity issue: 279455
Fixes: 05fa3d4a6539 ("bus/ifpga: add Intel FPGA bus library")
Cc: stable@dpdk.org

Signed-off-by: Rosen Xu <8f603db01337dbfe2ce4743ebc0cdbcec6fa456f@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk