ixgbe: add ixgbe_write_pci_cfg_word with ixgbe_removed check

Inline with the current use for ixgbe_read_pci_cfg_word, create a
similar function for writing PCI config, which checks whether the
adapter has been removed first, if Live Error Recovery has been enabled.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>