net/tap: fix null MAC address at init

net/tap: fix null MAC address at init

Immediately after init (probing), the device MAC address is all zeroes.
It should be possible to get a correct MAC address as soon as that,
without need for a dev_configure().

With this patch, a MAC address is set in eth_dev_tap_create()
explicitly. It either comes from the remote if any was configured, or is
randomly generated. In any case, the device MAC address is guaranteed to
be the correct one when the tap netdevice actually gets created in
tun_alloc().

Fixes: f76d46b4ff08 ("net/tap: add MAC address management")
Fixes: 2bc06869cd94 ("net/tap: add remote netdevice traffic capture")

Signed-off-by: Pascal Mazon <pascal.mazon@6wind.com>