ixgbe: pci_set_drvdata must be called before register_netdev

We call pci_set_drvdata immediately after calling register_netdev,
which leaves a window where tasks writing to the sriov_numvfs sysfs
attribute can sneak in and crash the kernel.  register_netdev cleans
up after itself so placing pci_set_drvdata immediately before it
should preserve the intent of commit 0fb6a55c ("ixgbe: fix crash
on rmmod after probe fail").

Fixes: 0fb6a55c ("ixgbe: fix crash on rmmod after probe fail")
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>