raw/ifpga: remove virtual devices on close

raw/ifpga: remove virtual devices on close

Virtual devices created on ifpga raw device will not be removed
when ifpga device has closed. To avoid resource leak problem,
this patch introduces an ifpga virtual device remove function,
virtual devices will be destroyed after the ifpga raw device closed.

Fixes: ef1e8ede3da5 ("raw/ifpga: add Intel FPGA bus rawdev driver")
Cc: stable@dpdk.org
Signed-off-by: Wei Huang <wei.huang@intel.com>
Acked-by: Tianfei Zhang <tianfei.zhang@intel.com>
Reviewed-by: Rosen Xu <rosen.xu@intel.com>