intel/igbvf: free irq on the error path in igbvf_request_msix()

In igbvf_request_msix(), irqs have not been freed on the err path,
we need to free it. Fix it.

Fixes: d4e0fe01 ("igbvf: add new driver to support 82576 virtual functions")
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Tested-by: Marek Szlosek <marek.szlosek@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>