[ Upstream commit c2f3b8e3 ]

The assertion of netif_device_present() at the top of
efx_hard_start_xmit() may fail if we don't do this.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
[bwh: Backported to 3.0: adjust context]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>