Samples: Enabled Network Shell with XGMAC ethernet.

Enabled Network shell and Ethernet L2 interface
with XGMAC driver in CLI application
Enabled MDIO shelll with dwcxgmac mdio driver.
Enabled TCP and  UDP over IPV4.

Added intel_socfpga socdk support for echo_client and
echo_server sample applications.

Signed-off-by: Santosh Male <santosh.male@intel.com>