global: Cleanup usage of "ETH_ALEN"

global: Cleanup usage of "ETH_ALEN"

The value of "ETH_ALEN" is defined to 6 in <linux/if_ether.h>. This file
is included in <net.h>. In the places where we had ETH_ALEN but no
direct include of <net.h>, add <linux/if_ether.h>. In the places where
we had a custom name used, make use of ETH_ALEN instead.

Signed-off-by: Tom Rini <trini@konsulko.com>