eth: fbnic: Add ethtool support for fbnic

Add ethtool ops support and enable 'get_drvinfo' for fbnic. The driver
provides firmware version information while the driver name and bus
information is provided by ethtool_get_drvinfo().

Signed-off-by: Mohsin Bashir <mohsin.bashr@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>