sfc: Change order of device removal to reverse of probe order

This makes efx_pci_remove_main() more obviously the inverse of
efx_pci_probe_main(), and matches our out-of-tree driver.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>