net/miiphy/serial: drop duplicate "NAMESIZE" define

net/miiphy/serial: drop duplicate "NAMESIZE" define

A few subsystems are using the same define "NAMESIZE".  This has been
working so far because they define it to the same number.  However, I
want to change the size of eth_device's NAMESIZE, so rather than tweak
the define names, simply drop references to it.  Almost no one does,
and the handful that do can easily be changed to a sizeof().

Signed-off-by: Mike Frysinger <[email protected]>