Commit 
c31e5f9 ('sfc: Add channel specific receive_skb handler and
post_remove callback') added the function pointer field
efx_channel_type::post_remove and an unconditional call through it.
This field should have been initialised to efx_channel_dummy_op_void
in the existing instances of efx_channel_type, but this was only done
in efx_default_channel_type.  Consequently, if a device has SR-IOV
enabled then removing the driver or device will result in an oops.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
 
 static const struct efx_channel_type efx_sriov_channel_type = {
        .handle_no_channel      = efx_sriov_handle_no_channel,
        .pre_probe              = efx_sriov_probe_channel,
+       .post_remove            = efx_channel_dummy_op_void,
        .get_name               = efx_sriov_get_channel_name,
        /* no copy operation; channel must not be reallocated */
        .keep_eventq            = true,