net: tg3: convert to hw_features

Cleanup hint: Some features are calculated in tg3_get_invariants() and
the rest in its caller --- tg3_init_one(). This is not changed here.

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Acked-by: Matt Carlson <mcarlson@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>