i40e: clear __I40E_VIRTCHNL_OP_PENDING on invalid min Tx rate

In the case of an invalid min Tx rate being requested
i40e_ndo_set_vf_bw() immediately returns -EINVAL instead of releasing
__I40E_VIRTCHNL_OP_PENDING first.

Signed-off-by: Stefan Assmann <sassmann@kpanic.de>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>