e1000: fix return value not set on error

Dean noticed that 'err' wasn't being set when the "goto err_dma"
statement is executed in the following hunk from the commit. It's value
will be zero as a result of a successful call to e1000_init_hw_struct().

This patch changes the error condition to be correctly propagated.

CC: stable@kernel.org
Signed-off-by:  Dean Nelson <dnelson@redhat.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Emil Tantilov <emil.s.tantilov@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>