net: xilinx: Remove unnecessary temac_property in the driver

This property is no longer used in the code yet the code looks for it in the device tree.
It does not cause an error if it's not in the tree.

Signed-off-by: Kedareswara rao Appana <appanad@xilinx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>