[PATCH] e1000: Added variable to handle return values for pci_enable_* functions

This was to fix compilation warnings.  Also added log messages when pci_enable_* functions return with an error.

Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: John Ronciak <john.ronciak@intel.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>