raw/ifpga: fix build with optimization

raw/ifpga: fix build with optimization

Compile failed with cflag optimization=1 on Ubuntu20.04 with GCC10.3,
it reported vendor_id and dev_id may be used uninitialized in function
ifpga_rawdev_fill_info().
Actually it's not the truth, the variables are initialized in function
ifpga_get_dev_vendor_id(). To avoid such compile error, the variables
are initialized when they are defined.

Fixes: 9c006c45d0c5 ("raw/ifpga: scan PCIe BDF device tree")
Cc: stable@dpdk.org
Signed-off-by: Wei Huang <wei.huang@intel.com>
Acked-by: Tianfei Zhang <tianfei.zhang@intel.com>
Acked-by: Rosen Xu <rosen.xu@intel.com>