net: netsec: remove static declaration for netsec_set_tx_de()

On commit ba2b2321

 ("net: netsec: add XDP support") a static
declaration for netsec_set_tx_de() was added to make the diff easier
to read.  Now that the patch is merged let's move the functions around
and get rid of that

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>