net: Check network device driver name

If name is longer than allocated space NAMESIZE
mac address is rewritten which show error
message like:

Error message:
Warning: Xlltemac.87000000 MAC addresses don't match:
Address in SROM is         30:00:00:00:00:00
Address in environment is  00:0a:35:00:6a:04

NAMESIZE contains Driver name + zero terminated character.

Signed-off-by: Michal Simek <monstr@monstr.eu>