net: bcmgenet: set Rx mode before starting netif

This commit explicitly calls the bcmgenet_set_rx_mode() function when
the network interface is started. This function is normally called by
ndo_set_rx_mode when the flags are changed, but apparently not when
the driver is suspended and resumed.

This change ensures that address filtering or promiscuous mode are
properly restored by the driver after the MAC may have been reset.

Fixes: b6e978e5 ("net: bcmgenet: add suspend/resume callbacks")
Signed-off-by: Doug Berger <opendmb@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>