bus/ifpga: remove useless check while browsing devices

bus/ifpga: remove useless check while browsing devices

reported by code analysis tool C++test (version 10.4):

  /build/dpdk-20.11/drivers/bus/ifpga/ifpga_bus.c
  67    Condition "afu_dev" is always evaluated to true
  81    Condition "afu_dev" is always evaluated to true

The "for" loop already checks that afu_dev is not NULL.

Fixes: 05fa3d4a6539 ("bus/ifpga: add Intel FPGA bus library")
Cc: stable@dpdk.org
Signed-off-by: Maxime Gouin <maxime.gouin@6wind.com>
Reviewed-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Kevin Traynor <ktraynor@redhat.com>
Acked-by: Rosen Xu <rosen.xu@intel.com>