i40e: fix xdp handle calculations

Commit 4c5d9a7f ("i40e: fix xdp handle calculations") reintroduced
the addition of the umem headroom to the xdp handle in the i40e_zca_free,
i40e_alloc_buffer_slow_zc and i40e_alloc_buffer_zc functions. However,
the headroom is already added to the handle in the function i40_run_xdp_zc.
This commit removes the latter addition and fixes the case where the
headroom is non-zero.

Fixes: 4c5d9a7f ("i40e: fix xdp handle calculations")
Signed-off-by: Ciara Loftus <ciara.loftus@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

drivers/net/ethernet/intel/i40e/i40e_xsk.c

@@ -192,9 +192,9 @@ static int i40e_run_xdp_zc(struct i40e_ring *rx_ring, struct xdp_buff *xdp)
 {
 	struct xdp_umem *umem = rx_ring->xsk_umem;
 	int err, result = I40E_XDP_PASS;
-	u64 offset = umem->headroom;
 	struct i40e_ring *xdp_ring;
 	struct bpf_prog *xdp_prog;
+	u64 offset;
 	u32 act;
 
 	rcu_read_lock();
@@ -203,7 +203,7 @@ static int i40e_run_xdp_zc(struct i40e_ring *rx_ring, struct xdp_buff *xdp)
 	 */
 	xdp_prog = READ_ONCE(rx_ring->xdp_prog);
 	act = bpf_prog_run_xdp(xdp_prog, xdp);
-	offset += xdp->data - xdp->data_hard_start;
+	offset = xdp->data - xdp->data_hard_start;
 
 	xdp->handle = xsk_umem_adjust_offset(umem, xdp->handle, offset);