igb: Fix an error handling path in 'igb_probe()'

If an error occurs after a 'pci_enable_pcie_error_reporting()' call, it
must be undone by a corresponding 'pci_disable_pcie_error_reporting()'
call, as already done in the remove function.

Fixes: 40a914fa ("igb: Add support for pci-e Advanced Error Reporting")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Tested-by: Tony Brelinski <tonyx.brelinski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>