net: Increase ethernet name string size to 20 chars

net: Increase ethernet name string size to 20 chars

The 16 char ethernet name size is inadequate to hold the name of ethernet
name "DPMAC17@rgmii-id", which is a valid name in LX2160AQDS/LX2160ARDB.

Therefore, increase the name string size to 20 chars.

Reported-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Suggested-by: Ioana Ciocoi Radulescu <ruxandra.radulescu@nxp.com>
Signed-off-by: Pankaj Bansal <pankaj.bansal@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>