e100: fix build warning

In function 'e100_hw_init':
warning: 'err' may be used uninitialized in this function

Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>