net: broadcom: bcm4908_enet: fix minor typos

1. Fix "ensable" typo noticed by Andrew
2. Fix chipset name in the struct net_device_ops variable

Suggested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>