sfc: remove redundant variable old_vlan

Variable old_vlan is being assigned but is never used hence it is
and can be removed.

Cleans up clang warning:
warning: variable 'old_vlan' set but not used [-Wunused-but-set-variable]
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/ef10_sriov.c

@@ -564,7 +564,7 @@ int efx_ef10_sriov_set_vf_vlan(struct efx_nic *efx, int vf_i, u16 vlan,
 {
 	struct efx_ef10_nic_data *nic_data = efx->nic_data;
 	struct ef10_vf *vf;
-	u16 old_vlan, new_vlan;
+	u16 new_vlan;
 	int rc = 0, rc2 = 0;
 
 	if (vf_i >= efx->vf_count)
@@ -619,7 +619,6 @@ int efx_ef10_sriov_set_vf_vlan(struct efx_nic *efx, int vf_i, u16 vlan,
 	}
 
 	/* Do the actual vlan change */
-	old_vlan = vf->vlan;
 	vf->vlan = new_vlan;
 
 	/* Restore everything in reverse order */