net: fix eth.c kernel-doc warning

From: Randy Dunlap <rdunlap@xenotime.net>

Fix new kernel-doc warning in eth.c:

Warning(net/ethernet/eth.c:237): No description found for parameter 'type'

Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: David S. Miller <davem@davemloft.net>