Enabling SRIOV while the ixgbevf driver is loaded will result in all
mailbox requests from ixgbevf_open() being rejected by ixgbe because
adapter->clear_to_send is set to false on reset.

Call ixgbe_sriov_reinit() before pci_enable_sriov() to make sure that
mailbox requests are handled from the time ixgbevf is loaded.
Reported-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>