net: gem: Remove WRAP bit from TX buffer description

Removing this bit causes that frame is sent only once.
(With wrap big one packet has been sent several times
which dramatically decrease throughput)

TRM: (Table 16-3: Tx Buffer Descriptor Entry)

Signed-off-by: Michal Simek <monstr@monstr.eu>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Tom Rini <trini@ti.com>