ixgbe: fix crash on rmmod after probe fail

The driver has logic to free up used data in case any of the checks in
ixgbe_probe() fail, however there is a similar set of cleanups that can
occur on driver unload in ixgbe_remove() which can cause the rmmod command
to crash.

This patch aims to fix the logic by moving pci_set_drvdata() after all error
checks and then adds a check in ixgbe_remove() to skip it altogether if
adapter comes up empty.

Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>