net: xilinx_emaclite: Fix problem with first incoming packet

You can't ping the board or connect to it unless you send
any packet out from board.

Tested-by: John Williams <john.williams@petalogix.com>
Signed-off-by: Michal Simek <monstr@monstr.eu>
Acked-by: John Linn <john.linn@xilinx.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>