zynq: gem: Setting up WRAP bit for one TX bd

zynq: gem: Setting up WRAP bit for one TX bd

Setting up WRAP bit to indicate that this is the last TX BD in the
chain. On ZynqMP this problem was workaround by enabling TX_EN bit for
every packet send by "zynqmp: gem: GEM changes to make it work on ep108
RTL 3.1" (sha1: 01cf5de125122a10c8ceecd1ae4c1a13cb10f45c)

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Punnaiah Choudary Kalluri <punnaia@xilinx.com>